Bid-bots have become an essential part of steemit environment. Users use them to promote their post, to increase their reputation etc. However, I think only bid-bots cannot make a post profitable because lots of people are using them and the voting share is divided to such an extent that the received value of the bot's voting becomes a matter of loss. But, these top paid users are earning a lot by other users' herd mentality. When people see that some post is becoming popular, they also upvote that post, in a hope to get some curation reward. But they don't think that curation reward depends on the timing. The last voters do not get much.
If I am wrong, please correct me.