You can guess from the number of reviews and downloads as they change over time. Everyone says it "doesn't work" yet people still download and try it, which means they paid for it. Granted some might chargeback and refund, but not all. Also my personal experience as the owner of such listings is that you get about 1 review per hundred customers (unless you have a very pushy review process). I've made thousands of sales with only a dozen reviews. Also I'll admit to once having an app on a marketplace that was never updated and barely worked still making hundreds of dollars a month almost a decade later.
Given how easy it is to get a refund for an app purchase, I would be really surprised if this results in a significant revenue stream, but I don't actually know, of course.
Warren Buffett has a term for this, it's called "float". At my current (active, not abandoned) startup, my guess is somewhere around 30% of active paying customers are also non-users. Lots of industries have this. The majority of gym membership sales (50%+) and even a significant number of airline tickets are unused.