How to Fix a Shop Quantity Selector Charging for One but Granting Many

A quantity stepper that grants ten items but only charges for one is an instant economy exploit. Charging unit price times quantity and granting that same quantity fixes it. Here is how.

How to fix it

1. Charge for the quantity

Compute the total cost as unitPrice * quantity and deduct that, not the per-unit price, before granting the stack.

2. Validate the full cost

Check that the wallet covers the total cost for the selected quantity; reject or clamp the quantity if it does not.

3. Keep grant and charge in sync

Use the same quantity value for both the deduction and the grant, derived from one source, so they cannot diverge.

4. Bound the quantity

Clamp the selector to a sane maximum (stock, inventory space, affordable amount) so an extreme value cannot overflow the cost or the inventory.

Catching the ones you can't reproduce

The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.

Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.

This is where a tool like Bugnet earns its place. Its SDK captures every Unity error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.