Latest / The Newsletter Podcast with Fexingo: Substack, Beehiiv, and Email Newsletter Business / Why Newsletters Are Building Private Marketplaces
Transcript
- Lucas: So earlier this week I got a pitch from a newsletter I read pretty regularly — it's a B2B SaaS analysis, about 50,000 subscribers. The pitch wasn't for a sponsorship slot. It was an invitation to join what they're calling their 'private marketplace.' Luna: Private marketplace — like the programmatic ad world uses that term, right? Where publishers offer premium inventory to a select group of buyers? Lucas: Exactly. In display advertising, a private marketplace — or PMP — is basically an invite-only auction. But this newsletter was doing it for email sponsorships. They'd built a pool of about a dozen regular advertisers, each paying a flat monthly fee for a guaranteed number of placements across their issues. Luna: So instead of selling individual sponsorships week to week, they're selling an ongoing commitment. That's a big shift from how most newsletters operate. Lucas: It is. And it's becoming more common. I've now seen at least five newsletters in the past few months that are moving away from the 'one sponsor per issue, first-come-first-served' model toward something more structured. The economics are pretty interesting. Luna: Walk me through the numbers. How does a private marketplace change the math for a newsletter writer? Lucas: So let's take that B2B newsletter. They were charging around $2,000 per sponsored mention before — that's a typical CPM of about $40 for a 50,000-subscriber list with a 40 percent open rate. Decent, but not premium. Luna: Right, and that's if they sell every slot. Lots of newsletters have inventory that goes unsold. Lucas: Exactly. By creating a private marketplace with, say, eight advertisers each paying $5,000 a month for a guaranteed two mentions, they lock in $40,000 in recurring revenue. That's more predictable than chasing 20 individual deals at $2,000 a pop. And the CPM effectively rises because they're selling a bundle. Luna: But the advertiser gets something too — guaranteed placement, probably first pick of which issue they appear in. It's a relationship, not a transaction. Lucas: Exactly. And that's the key insight. Advertisers in these private marketplaces are often willing to pay a premium because they know exactly what they're getting. The newsletter writer curates the pool, so there's less risk of their ad running next to something that doesn't fit. Luna: It also means the writer has to manage relationships more actively. You can't just send a rate card and hope someone bites. You're essentially running a small ad sales team. Lucas: That's the trade-off. But there's another layer: some newsletters are forming collectives to create shared private marketplaces. I spoke with a group of five finance newsletters last month — they each have between 30,000 and 80,000 subscribers. They pooled their inventory and started selling access to advertisers who want to reach a combined audience of about 300,000 finance-interested readers. Luna: So they become a mini ad network, basically. That's a way to compete with the big platforms. Lucas: Right. And they're using tools like Passionfroot and Swapstack to manage it — platforms that let publishers set up a marketplace, invite advertisers, and handle the transaction. Some are even using first-party data to offer targeting: 'run your ad only to subscribers who opened the last three issues' or 'only to subscribers who clicked on a finance link.' Luna: That's interesting because it's essentially what programmatic does, but within a trusted environment. The advertiser gets better targeting, the publisher controls the data. Lucas: And the CPMs can double. I've seen some private marketplace placements go for $80 to $100 CPM, versus maybe $30 to $50 in an open sponsorship. The scarcity and the relationship drive the price up. Luna: But there's a risk: if you create a private marketplace, you might alienate smaller advertisers who can't commit to a monthly retainer. Does that create a two-tier system? Lucas: It can. Some newsletters run a hybrid model: they keep a few slots open for one-off sponsors at a lower rate, and reserve the premium slots for the marketplace. Others just go all-in on the marketplace and turn away ad-hoc inquiries. Luna: Which one do you think is smarter? Lucas: For most newsletters under 50,000 subscribers, I'd say a hybrid. You don't want to lose the revenue from an unexpected opportunity. But for a newsletter that's already hit a certain scale — say, 100,000 plus — the predictability of a private marketplace is really valuable. You can plan editorial around it. Luna: And you can raise rates over time. Once advertisers are locked into a monthly commitment, it's easier to increase prices as your list grows. Lucas: Exactly. I know one newsletter writer who started with a private marketplace at $3,000 a month per advertiser. Six months later, after adding 15,000 subscribers, she bumped it to $4,500. The advertisers stayed because the audience quality was there and they'd already built a relationship. Luna: That's a 50 percent increase in six months. Hard to do with one-off sponsorships. Lucas: And the interesting thing is that the infrastructure for this is getting better. There are now platforms that let you automate the marketplace — manage invoices, track delivery, even do real-time reporting on opens and clicks per advertiser. It's becoming more like a proper business operation. Luna: So is this the future of newsletter monetization? Every newsletter eventually becomes its own ad network? Lucas: I think we'll see a bifurcation. The big players — the ones with 500,000-plus subscribers — will build their own in-house sales teams and private marketplaces. The mid-sized ones will join collectives. And the smaller ones will rely on networks like Swapstack or Letterwell for programmatic fill. Luna: What about the very small newsletters, like 5,000 subscribers? Can they participate? Lucas: They can, but the math is tougher. A private marketplace needs enough inventory to be worth an advertiser's time. If you only publish weekly and have 5,000 subscribers, you're probably better off with a sponsorship marketplace like SponsorshipHub or a direct one-off deal. But I'm seeing some collectives that include small newsletters too — they pool inventory and split revenue proportionally. Luna: That's a good model for the long tail. But it requires trust among the publishers. Lucas: It does. And transparency. The collectives I've seen use a shared dashboard where everyone can see how many impressions each newsletter delivered and how much revenue each advertiser paid. That builds trust. Luna: So what's the one thing a newsletter writer should do today if they want to start a private marketplace? Lucas: First, audit your current sponsors. If you have a few advertisers who keep coming back, pitch them on a monthly retainer. Offer a slight discount — say 10 percent — in exchange for a three-month commitment. That's your seed. Then you can open it to a few more advertisers who match your audience. Luna: And don't overfill. Part of the appeal is scarcity. Lucas: Right. You want advertisers to feel like they're in an exclusive club. That's what makes private marketplaces work. Luna: It's a smart evolution. And I think it reflects how newsletter advertising is maturing as a channel. Lucas: Agreed. And you know, speaking of maturity, we've been running this podcast without ads from day one — we deliberately keep it ad-free. If that kind of independent, sponsor-free content is valuable to you, and you want to support that choice, you can find us at buy me a coffee dot com slash fexingo. Luna: Yeah, it's a way to keep the show exactly as we want it — no outside pressure, just the conversations we think are worth having. Lucas: Exactly. So back to the private marketplace idea — I think the next frontier is programmatic direct for newsletters. Imagine an advertiser being able to bid in real time for a slot in a newsletter, but only if the publisher approves the creative. That's a hybrid that combines the efficiency of programmatic with the curation of a private marketplace. Luna: And it would solve the problem of unsold inventory. If a newsletter has a slot open two days before send, they could fill it programmatically at a lower price, rather than leaving it empty. Lucas: Exactly. A few platforms are already testing this. I think within the next year, most newsletters above a certain size will have some form of automated, curated ad selling. Luna: So the takeaway for a newsletter writer today: start building relationships with repeat sponsors, consider a monthly retainer, and keep an eye on the tools that are emerging. Lucas: And if you can, join or start a collective with peers in your niche. The combined reach is a powerful sell. Luna: I think that's the most actionable advice we've given in a while. Lucas: I'll take that as a compliment. Next week we'll look at how newsletters are using AI to write ad copy that sounds like the host — which raises some interesting ethical questions. Luna: Looking forward to that one.