Bounty minimum on other users' questions

Question

When we offer bounties on our own questions, we are given the options of 50-500 reputation in increments of 50. When offering bounties on questions posted by other users, the increment is the same, but starts at 100 instead of 50. Why is that?

Note: The FAQ states (emphasis from FAQ):

Slice off anywhere from +50 to +500 of your own hard-earned reputation and attach it to any question as a bounty.

EDIT (Feature Request):
Can we get a note added to indicate that this is the case when starting a bounty?

Answer 1

This change applies only to questions you've answered, and was made recently to dissuade users from attempting to gain reputation by manipulating the bounty system (the ethics of doing this are debatable, but that's neither here not there).