And someone would install random apps to save $5 on $100 purchases?

"random apps" and it's the largest eCommerce company on the planet

When I did customer tech support for a major retailer, we had confused customers calling all the time because they would randomly get price-match refunds they never asked for. They were installing apps that were automatically requesting the refunds by searching their emails for orders and checking the prices on the websites. These people had no idea they had even given these apps permission to read their emails.

You'd be surprised on what general public can go to save $5.

eBay keeps pushing their app with a $5 discount, advertised using a focus-stealing popup interrupting your attempt to give them money, so some people must be taking the bait.