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Don't know what I should think about those bots.
What's your opinion?

It seems that you are losing your money alot of times because there has been highly increased demand for them up-vote bots. @exyle speculated that reason for this high SBD is especially because of those bid-bots that accept only SBD. That grumpy cat down-votes posts that receive upvotes from bots that are willing to upvote content that is more than 3,5 days old.

Have you ever tried it yourself?
Who's that grumpy cat?

I have not tried, but i've seen some calculations. How those upvote-bots work is that there is a round when everyone can put their money in. The voting-power % that is used is calculated from your contribution to that bidding round compared to others. There has been increased demand for these bots which means that more people are participating into bidding rounds causing % upvote from that bot to be too small for profit in some cases. Check out https://steembottracker.com/
also check out @grumpycat for more info about what he is doing.

Thanks, I am gonna check it out!