It's a progressive charge. If you have more money to spend, a lot of the time you'll end up spending more on desserts, drinks, etc. Then you pay a greater amou

It's a progressive charge. If you have more money to spend, a lot of the time you'll end up spending more on desserts, drinks, etc. Then you pay a greater amount of money for the service. If you have less to spend, you'll buy fewer things, and pay a smaller charge.