What You Really Pay for Transactional Email (And Why BYO SES Quietly Wins on Cost)

A while ago, I was helping a team that sent a decent amount of transactional email : not millions, but enough that the monthly bill wasn’t trivial anymore. Something like 150k to 250k emails a month. Classic SaaS stuff: signups, verifications, invoices, password resets. The boring but critical pipes.

One day their founder forwarded me their invoice and wrote: “This feels… high?”

It wasn’t the first time I’d heard that. Every few months, some engineering team discovers that their transactional email bill has crept into “Why is this so pricey?” territory. It’s a weird moment because the service itself feels like a commodity. You fire an API request, an email goes out, and that’s that. So why does it cost hundreds of dollars? To answer it, we did the thing nobody thinks to do: we pulled up AWS SES pricing and compared it directly to the modern email API they were using. That’s when the conversation got interesting.

The raw cost — the thing nobody looks at first

If you’ve never read the AWS SES pricing page, it looks like something Amazon forgot to update:

10 cents per thousand emails.

Really. That’s it. No clever packaging. No multi-tier grids. No “email units.” Just a flat, boring, suspiciously cheap number.

We ran their volume through SES’s math:

• 100k emails → $10
• 200k → $20
• 500k → $50
• 1M → $100

This is the part where people usually say, “Wait, what?”. Because the bill they were actually paying every month (using Resend) looked more like:

• 100k → $90
• 200k → $160
• 500k → $350
• 1M → $650
• 2.5M → $1,050

And when you stack that against SES raw cost, the markup becomes almost absurdly clear:

• 100k: 9×
• 200k: 8×
• 500k: 7×
• 1M: ~6.5×
• 2.5M: ~4.2×

Sitting in that room, looking at those numbers, nobody said anything for a while.

How did we end up here?

Email providers aren’t charging you for sending email. They’re charging for everything wrapped around it. The dashboards, the API, templates, logs, incident handling, shared pool management, and so on. And that’s fine. Those things have real value. But the industry quietly built a habit around bundling the raw email cost inside a much larger package. You’re paying for the abstraction the same way you’d pay for managed compute or a managed database. Except, in this case the underlying cost is comically tiny.

What makes this different from compute or databases is that the underlying cost doesn’t balloon with scale. It stays stuck at: 10 cents per thousand emails, forever. So when your volume grows, you don’t get economies of scale, you get the opposite.

The upside-down cost curve

There’s this moment every growing company hits where their email bill starts looking wrong. It’s usually somewhere between 100k and 500k emails a month. Not huge enterprise volume just a healthy SaaS with real users. At that point, the unit economics shift enough that you can’t pretend they’re rounding errors.

Let’s use the actual numbers:

• Sending 500k emails
  • SES: $50
  • Resend: $350
• Sending 1M emails
  • SES: $100
  • Resend: $650
• Sending 2.5M emails
  • SES: $250
  • Resend: $1,050

The infrastructure cost is tiny. What you’re paying for is the packaging. And that’s where “Bring Your Own SES” enters the picture. It’s not as a clever hack, but as a model that actually respects how infrastructure pricing is supposed to scale.

BYO SES doesn’t make email cheaper — it makes pricing honest

This is the part people misunderstand. BYO SES isn’t some trick to outsmart email providers. It’s just a straight line between your usage and your cost.

When you bring your own SES account:

• You pay AWS for the raw send
• You pay an email platform only for the software layer
• The two bills stay separate
• The markup disappears
• The cost curve flattens
• You stop subsidizing other senders

That’s it. No magic. No loopholes. No special optimizations. You’re just removing the bundling layer that hides the sticker price.

And yes, this becomes more important as you grow

You don’t need to care about this at 3,000 emails. At 30,000 you start being mildly curious. At 100,000 you start running napkin math. At 500,000 you suddenly realize the numbers are large enough to take seriously. And by the time you hit 1–2M emails a month, you can’t ignore it. This is usually the exact moment engineering teams start asking: “Isn’t SES like a few cents? Why are we paying hundreds?” And the answer is: yes, SES is just a few cents.

The real takeaway

Transactional email isn’t expensive, the markup is. AWS SES is simple, boring, predictable, and brutally cheap. The moment you unbundle sending costs from the tooling layer, the pricing finally makes sense again. Whether you’re running a small product or something that’s growing fast, understanding the difference between raw sending cost and packaged sending cost is one of those things that stops being optional the moment your email bill tips past the “that seems high” threshold. The economics don’t lie. BYO SES isn’t about complexity, it’s about sanity.

Meta description

Discover the real cost of transactional email. A founder explains why AWS SES is dramatically cheaper than modern email APIs like Resend, how markups work, and why Bring Your Own SES (BYO SES) offers transparent, predictable pricing at scale.

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