LetterDuck vs Substack: the 10% cut against a flat $50
Substack costs nothing until you earn something, then takes 10% forever. The crossover point is a number you can compute. We computed it.
What each one is
Substack is a publishing network with the simplest deal in media: publish free forever, at any list size, with the website, podcast and video hosting, Notes, and the recommendations engine all included, and pay only when readers pay you. When they do, Substack keeps 10% of gross. The network is the product; the app, recommendations, and Notes drive real organic subscriber acquisition that a standalone email tool cannot, and a full export of your list and archive is free whenever you want it.
LetterDuck is email infrastructure you rent flat. $50 a month covers one domain end to end: unlimited addresses (each is a routing rule, not a seat), a threaded team inbox where anyone replies as any address on the domain, and a newsletter composer with a designed template. The deliverability layer is the point: SPF, DKIM, and DMARC configured on your domain, a coded warm-up throttle, automatic suppression, and RFC 8058 one-click unsubscribe stamped on every campaign. There is no revenue share because we never touch your revenue. LetterDuck is currently in waitlist mode, so the form below reserves a spot rather than opening an account.
What it costs at four list sizes
| Monthly cost at | Substack | LetterDuck |
|---|---|---|
| 500 subscribers | $0 | $50 flat |
| 1,000 subscribers | $0 | $50 flat |
| 5,000 subscribers | $0 | $50 flat |
| 10,000 subscribers | $0 | $50 flat |
Public list prices, August 2026, annual billing where offered. Substack: Substack does not charge by subscriber. A free newsletter costs nothing at any size; the cost is 10 percent of paid subscription revenue plus payment processing. LetterDuck is $50 per domain, flat, unlimited addresses and subscribers.
The cost story: show the math
Substack's fixed cost is zero, so the comparison is entirely about the revenue share. Here is the arithmetic, using the fee structure verified on substack.com/going-paid in August 2026.
The platform fee is 10% of gross. Set it against our flat fee:
0.10 x G = $50 -> G = $500/month gross paid revenue
At Substack's $5 minimum subscription price, $500 a month is exactly 100 paid subscribers. Below 100 paid readers, Substack's cut is smaller than our flat fee and Substack is the cheaper platform. Above it, every new paid reader widens the gap.
Follow the curve up. At 250 paid subscribers paying $5 a month, gross is $1,250 and the platform fee alone is $125 a month; combined with Stripe processing, total fees run about $245 a month. At $5,000 a month of gross revenue, Substack's 10% is $500 a month, more than the priciest published flat-rate plans at Ghost or beehiiv, and it does not stop there because a percentage never does.
Two honest footnotes to that math. First, Stripe is not the differentiator: if you charge readers through your own Stripe account you pay 2.9% + $0.30 yourself, so the fair comparison is the 10% against the $50, with Substack's extra 0.7% recurring billing fee as the only processing difference (that fee quietly rose from 0.5% in July 2024, and grandfathered pricing ended June 30, 2025). Second, annual subscriptions soften Substack's bite: a $50-a-year subscription loses $7.10 to fees, 14.2% instead of 19.6%, because the fixed $0.30 dilutes over a bigger charge.
And the deepest honesty: LetterDuck has no paid-subscription machinery at all. Substack gives you paywalls, tiers, and billing with zero setup. Leave, and gating your paid content becomes your problem, on your own billing stack. For how publishers structure that on infrastructure they own, see our pillar on running a newsletter on your own domain.
Feature by feature
| Capability | Substack | LetterDuck |
|---|---|---|
| Fixed monthly cost | $0 at any list size, forever | $50/domain flat |
| Cut of paid-subscription revenue | 10% + Stripe, ~19.6% all-in on a $5 sub | 0%; we never touch revenue |
| Discovery: recommendations, Notes, the app | Real organic acquisition | |
| Paid-subscription billing built in | Paywalls, tiers, founding members | Bring your own billing |
| Podcast and video hosting | Included free | |
| Hosted website | Custom domain is a one-time $50 per publication | Not a website builder |
| Email addresses on your own domain, send and receive | Unlimited, included | |
| Team inbox for reader replies | Threaded, reply as any address | |
| Automations and sequences | None | None here either |
| Segmentation and A/B testing | Limited | Folders and notes, no A/B |
| List portability | Free full export of list and archive | Your list, exportable, on your domain |
| Deliverability under your control | Rides Substack's domain reputation | SPF, DKIM, DMARC, warm-up, suppression on yours |
Choose Substack if
- You are starting from zero. No other platform lets you publish, host a podcast, and charge readers with literally no up-front cost.
- Discovery matters more than margin right now. Recommendations, Notes, and the app surface writing to readers you have never met; we surface nothing to anyone.
- Your paid revenue is under about $500 a month. Below the crossover, the 10% deal is genuinely the better deal.
- You want billing handled entirely. Paywalls, annual plans, and founding tiers work on day one with no Stripe configuration.
Choose LetterDuck if
- Your paid revenue is comfortably past $500 a month and compounding. At $5,000 a month gross, switching converts a $500 monthly platform fee into a $50 one.
- You want the publication's email to live at your domain, not around it. Reader replies land in a shared inbox your whole team can answer from editor@, tips@, or any address you invent, at no per-address cost.
- Sender reputation should be an asset you own. On Substack your mail rides their infrastructure; here your domain earns its own record, with a throttle that ramps roughly 150 sends on day one to about 1,100 a day by day seven and a send path that halts itself at a 0.3% complaint rate.
- You are a working newsletter creator who already has an audience and wants a flat, boring bill.
If neither fits cleanly, the broader field is mapped in our Substack alternatives guide.
Migrating from Substack to LetterDuck
A free publication moves in an afternoon plus a warm-up week. A paid publication is a different animal: the list moves fast, the billing relationship does not, so budget weeks for a paid migration and plan the announcement before the move.
- Export everything from Substack's settings. The export is free and complete: subscriber CSV plus your full post archive. This is Substack's most underrated feature and you should use it even if you stay, as a backup.
- Import the CSV into LetterDuck. Import your active list; leave long-dead addresses behind, because a fresh domain's reputation is built by engaged recipients, not by list size.
- Verify your sending domain. You add a handful of DNS records (we provide the exact values) and every campaign then goes out with authentication and one-click unsubscribe headers already stamped:
List-Unsubscribe: <https://yourdomain.com/u/...>, <mailto:unsub@yourdomain.com>
List-Unsubscribe-Post: List-Unsubscribe=One-Click
- Warm up before the first full send. The throttle spreads a large first send automatically, taking the lower of its ramp curve and the relay ceiling. That ceiling is 95 a day on our current plan, so a 10,000-subscriber list takes months of daily sends, not a week. Plan the migration around it.
- If you charge readers, rebuild billing before touching the list. Set up your own payment flow, tell paid readers what changes and when, and only then redirect the publication. The tooling transfer is trivial; the money transfer is the project.