Depends on your product, model, and demographic.

At work our refund rate is like 30% for Japan. Investigating this, it turns out there is a cultural behaviour where converting at a higher rate early and refunding if it's not a good fit is the normal way of doing things.

And in a past life, general 4% refund/return rate is pretty common across most ecom markets.

Not saying apps are in this boat but if you ignore refunds in business you're in for a bad time.

Or a userbase that for some reason dislikes and abuses you. Maybe you have made enemies because of some random political statemant. A large enough group could ruin you.