I used vote bidding bots over the week.
My conclusion is simple: they won't make your money back.
Let's take my post for example:
https://steemit.com/bwphotocontest/@sulev/my-favorite-images-so-far-b-and-w-photo-contest-3
I payed 45 SBD to to upvote my post.
gave me a vote worth 83$.
In 6 days I will receive 75% of the payout: 32,2SBD and 8,74SP.
So what's going on here?
I'm pretty sure Steemit still counts 1SBD equal to 1$. If I subtract the SBD payout from the $ payout and divide it with the STEEM payout amount I'm left with about 3,7, which is precisely the average cost of STEEM for the past week.
Simply put: you pay 1SBD to a votingbot. It will upvote your post with a 2$ vote. Steemit will pay you 2$ worth of SP and SBD, while you original 1SBD was worth almost 4$ on the exchange.
This leads to a simple conclusion: as long as SBD is worth more than 1$, bidding bots will not make your money back, you will lose money instead. The whales are scamming you.
I was foolish enough to try these bots out before investigating the mechanisms behind it. Don't send your money to bots unless you are desperately looking to get on the trending page.
Stay safe!