Good thing you noticed this as I was just about to use it!

I checked the bids and while doing it I think I also figured how to accurately determine if the bid brought net profit: after the received bid, the author rewards (0,75 x POST REWARDS) should be bigger than the AUTHOR REWARDS that would've been received without the ocdb vote + the bid amount.

Put into a formula it looks like this:

0.75 x POST REWARDS > ((POST REWARDS - ocdb vote value) x 0.75) + bid value)

^{where (POST REWARDS - ocdb vote value) x 0.75 determines the original AUTHOR REWARDS a user would've received without the ocdb vote.}

So, if the above formula holds TRUE, then the bid brings net profit, but of course this is with the assumption that the numbers are static – which they aren't, they seem to be changing: the post you used as an example is now 78.07 (STU) on Steempeak interface which I think is equivalent to SBD.