Of course, bounty campaign requires periodical time investments on dev's part, but I've seen how much attention such campaign could bring. Human resources are much more valuable than time, don't forget that!
Exactly! Huge amount of reposts/retweets can promote company as well as satisfy people's lust for money, that's the way how bounty campaign works!
There are many paths one can take to achieve that goal, but from what I've seen so far, this is the best way when talking about how much investors should invest both money and/or time.