Probably, I am doing something wrong. But so far I somehow always ended up with by far less as actual reward payout for my upvote bot treated posts than the number below the article claimed it to be.

You are not doing anything wrong but it's the actual fact.
I've tried almost all of those upvote bots but none of them gave profit...Now I have almost stopped using them, I prefer to buy steem and power up with the SBDs rather than giving it to upvote bots.