The first question that decides a Shopify app's cost is not what it does — it is who it is for. An app built for one store, to solve one merchant's problem, is a fundamentally different project from an app you list on the App Store for thousands of strangers to install. Same platform, same APIs, wildly different budgets, because the second one has to handle every store's quirks, survive Shopify's review, and bill money reliably.
So before anyone quotes a number, that fork has to be settled. Here is how the cost actually assembles on each side of it, what pushes it up, and roughly where the tiers land. Duskel builds Shopify apps from around $3k for a focused custom app, with public App Store products running far higher for reasons I will make concrete.
Private and custom apps versus public apps
A custom app is built for a single store or a single organisation. It does not go through App Store review, it does not need public billing, and it only has to work against one store's actual data and theme. That containment is the whole reason it is cheaper — you are solving a known problem for a known setup, not defending against every configuration on the platform. Most "we just need Shopify to do this one thing" requests live here.
A public app is a product. It installs on any store, so it has to cope with themes you have never seen, data at volumes you cannot predict, merchants who will use it in ways you did not intend, and Shopify's App Store review standing between you and every user. It needs onboarding, support, a billing system, and a level of polish that a private tool can skip. It is not a bigger version of a custom app; it is a software business with a Shopify-shaped front door.
What actually drives the price
Scope of the Shopify surface is the first driver. Reading and writing products or orders through the Admin API is well-trodden and bounded. Touching checkout, injecting into the storefront, building theme app extensions, handling webhooks reliably, or reaching into Shopify's newer extension points is more work and more edge cases. The more of Shopify's surface your app has to hold correctly, the higher the number.
A back end is the second, and usually the largest. An app that only reads and displays data is small. An app that stores its own data, keeps state in sync with the store, processes webhooks, and does real work on its own server is mostly a back end that happens to plug into Shopify. Accounts, a database, hosting, and keeping in sync when Shopify sends you a change are where the engineering time concentrates.
The third is anything real-time or high-volume: syncing large catalogues, reacting to orders as they happen, handling stores that do serious traffic. Correctness under load and staying consistent with Shopify when webhooks arrive out of order or get missed entirely is genuinely hard, and it is the part that separates a demo from something a busy merchant can trust.
The billing API and App Store review
If your app is public and charges money, you do not get to bolt on Stripe and call it done — Shopify requires you to bill through its Billing API for most cases, taking payment through the merchant's existing Shopify relationship. That means building against recurring charges, usage charges, trials, and plan changes, and handling every state those can be in. It is not enormous, but it is real, mandatory work that a private app skips entirely, and it has to be right because it is money.
Then there is review. A public app has to pass Shopify's App Store review, which checks functionality, performance, the OAuth and permission flow, and adherence to their requirements. It can take iterations, each round has a wait, and a rejection sends you back to fix and resubmit. You budget both the engineering to meet the bar and the calendar time to get through the queue. A custom app avoids all of this, which is a meaningful part of why it is cheaper and faster.
The cost tiers, honestly
Connector, from around $3k: a focused custom app that syncs Shopify with one other system, automates a specific task, or exposes data the merchant needs. One store, no App Store review, no public billing, a bounded slice of the Admin API. This is the tier most single-store requests actually sit at, and it is a matter of weeks rather than months.
Full SaaS app, $20k to $100k and up: a public App Store product with accounts, its own back end, the Billing API, onboarding, support, and enough robustness to install cleanly on any store and pass review. The wide range is honest — it depends almost entirely on how much back end sits behind it and how much of Shopify's surface it has to hold. A narrow public app is near the bottom; one syncing large catalogues in real time across many stores is near the top and beyond.
The cheapest way to be wrong here is to build a public app when you needed a private one. If the goal is to solve your own store's problem, a custom app does it for a fraction of the cost and none of the review. Only pay for the public tier when the product itself — sold to other merchants — is the actual point. Prove the idea on one store first; the App Store will still be there when you have earned the reason to be on it.