Actually it seems like a discrepancy between Bitcoin and USDT. If you look at the USD only it says 547 was the high on USDT charts. Of you look at the USD value of bitcoin that you would have 600$. Even now if you look at Bittrex the USDT price is like 16 dollars lower than then the value of the Bitcoin you would receive. Something I just noticed. So now I have a question are you better off trading to Bitcoin and then trading for USDT? Something I may try in the future to see how it works out.