The most expensive bug I've ever fixed didn't crash anything. The button worked. The screen loaded. Support got zero tickets.
It was a subscription flow quietly converting far fewer people than it should have — losing paying customers at the exact moment they'd decided to pay.
Revenue bugs break quietly
This is the trap with purchase flows: when they break, they usually don't break loudly. No error, no crash report. Just a number that's lower than it should be, and no one knows why. Everyone assumes it's the price, the market, the funnel. It's often the code.
When we diagnosed and fixed the defects in that flow, free-to-paid conversion went up 20%. Same traffic. Same price. Same product. We just stopped losing people who were already trying to give us money.
The question worth asking
If you run a subscription app, ask your team this: when did we last watch a real user go through the entire purchase flow, on a real mid-range device, start to finish?
Not the happy path in a demo. The real thing, with a flaky network and an interrupted payment. That's usually where the money is hiding.