The most expensive song I have played

[Ben and a couple friends eating in a restaurant on the tallest building in Nanjing, Ben found there was a piano nearby and offered to play a song.]

V: (to the waitress) Hi, can we use the piano over there?

Waitress: Yes, you can, 50 RMB.

Ben: You pay me?

Waitress: No, you pay it.

Ben: For as long as I can?

Waitress: For one song only, you have to pay another 50 for a second song.

[Ultimately the group decided to pay the 50 RMB anyways, and Ben played a song on the piano for 2 minutes.]

[Q suggested paying another 50 RMB for him to play the piano (which is basically making some noise), and let the waitress beg him to stop by paying him 100 RMB. Somehow this idea wasn't implemented. ]