I think it highly depends on how well you choose the bounties you participate in. They usually pay percentage of their ICO, so the more successful project you choose, the more you earn. The rewards can thus vary widely, probably somewhere between $100 - $10k per let's say 3-months running bounty campaign.
I agree with your opinion. it all depends on us to join in the gift or other projects. indeed if you join the gift of a willingness to pay certainly also many rewards. Because of the many choices of ICO.