The other twist to this of course is when people are spending other people's money or when they are being treated. Each situation is different. An offer to take

The other twist to this of course is when people are spending other people's money or when they are being treated. Each situation is different. An offer to take 10% a check if it is on an expense account is not the same as giving something to someone that is a bonus to them personally. I guess the best way to illustrate this would be with a hotel. Upgrading someone to a better room (at the same price) benefits them personally. Discounting the bill in that case generally would not be the same benefit or cause the same happiness to them.