"In choosing the $3.50 figure, I wanted to ensure it was a number that was inconsequential to a legitimate user of the service. That's about what a latte costs at my local coffee shop so spending a few bucks a month to search through billions of records seems like a pretty damn good deal, especially when that rate limit enables 57.6k requests per day."
https://www.troyhunt.com/authentication-and-the-have-i-been-...
"In choosing the $3.50 figure, I wanted to ensure it was a number that was inconsequential to a legitimate user of the service. That's about what a latte costs at my local coffee shop so spending a few bucks a month to search through billions of records seems like a pretty damn good deal, especially when that rate limit enables 57.6k requests per day."