After the Internal Median Price got stuck, bots on SBT were very unprofitable. Bidders were actually losing with every bid. After update all bots were suddenly profitable. Profit of 40% was no exception. The overwhelming of the bots have adjusted to the situation. But SBT still shows incorrect numbers so bots with no fixed profit on votes are not shown properly. That is all I know. Your 51$ vote is actually worth about 30 USD. But according to SBT, it is 23 USD.
For now, SBT has unfortunately no competition so we kinda have to use it.