Ahhh that's a whole different enchilada! If you told me that bribery in which money changes hands generally has a higher incidence when the briber is significantly wealthier than the bribee and can provide a monetary amount worth while for the party accepting the bribe, I would definitely have to agree with you.

A valet parking employee might get 'bribes' from different people to fetch their car first in the queue, such people might be DHH waiting for his custom Zonda HH (and giving the valet a 50), me waiting for my 335i (and giving the valet a 10 dollar bill), or the dude next to me that earns as much as the valet waiting for his Corolla (giving the valet a 5 dollar bill). The catch is that to bribe people with money, you need to have money to 'throw away' so to speak. Any one with sufficient disposable income can bribe a valet, and most that can actually do in some way or another, but how do the car and money less bribe a valet and why should they since they don't have a car anyways?