What Rebuy's Monthly Fee Actually Pays For (and When a Custom Function Is Cheaper)

Every Shopify merchant running upsells has done this math: the app works, revenue is up, and the invoice climbs anyway. Rebuy, like most upsell platforms, prices by order volume. Succeed harder, pay more. A store doing mid four figures of orders a month sits in the $250-$750/month band, and the number never goes down.

Here's the part that took us a while to say out loud: almost none of that fee is for the software. The widget code (a cart drawer, a "you might also like" block, a bundle discount) was written years ago and amortized long ago. What you're renting, month after month, is four operational things:

1. Uptime. Someone's servers render those widgets on every visit.
2. Compatibility. Shopify retires an API version every quarter, on a published schedule. Code that nobody updates stops working within a year, not because it broke, but because the platform moved underneath it.
3. Monitoring. When a discount misfires at 2am, it's their pager, not yours.
4. Support. A human answers when the widget looks wrong.

That's a fair thing to charge for. The question is whether it's fair at a price indexed to your order volume, for widgets that are the same code serving ten thousand other stores.

The alternative: own the widgets, rent the operations

Shopify quietly made a different model possible. Shopify Functions run discount logic inside Shopify's own infrastructure. Your bundle pricing executes on their servers, at checkout, with no third-party runtime in the money path. Checkout UI extensions render blocks the same way, edge-delivered. For a custom build, the recurring infrastructure cost of an upsell stack collapses to almost nothing, because Shopify is doing the serving. What Shopify Functions can actually do is the map; this post is the pricing argument.

So the honest pricing model splits in two:

• The build, billed once. Your widgets, your discount logic, tailored to your catalog instead of generalized for everyone's. You own the code outright.
• The care plan, billed monthly at a flat rate: hosting for the admin/analytics side, monitoring on the money path, the quarterly Shopify API upgrades, and support. The same four things the SaaS fee bought, without the software rent or the volume tax.

Our Checkout Suite Care Plans run $25-$99/month depending on what's actually deployed. Compare that to a volume-indexed $250-$750 and the payback math on a custom build is usually measured in months. And when a store cancels, the widgets keep running. The code is theirs. That's not generosity; it's what "you own the build" has to mean for the model to be honest.

When the SaaS is still the right call

Custom isn't always the answer. If you're iterating weekly on merchandising rules, want a marketer-driven drag-and-drop editor, or your upsell logic is genuinely generic, take the app, it's good software. The custom path wins when the logic is yours: paired-product bundles with subscription semantics, discounts gated on trusted metafields instead of tamperable cart attributes, offers that need your fulfilment data. That specificity is what a rented widget can never quite reach, and it's exactly the code you should own.

Caffeine and Commerce builds custom checkout suites for Shopify and Shopify Plus stores. If your upsell bill scales with your success, we should talk.