What is a typical donation?

[scrappyd]

I apologize if this is posted somewhere, I did search the forums but didn't find anything. I was just wondering what the typical donation is? Also if someone is doing personalized themes with different names in it, how much of a donation is typical for that? What if you request a person to provide a new type of theme (i.e., zen instead of today).

I was also curious, when you hit the "Thanks" button, do the theme builders get anything or is it just so they known how many people downloaded their theme?

Thanks!