Try them all (which you say you did), one of them "should" provide you some sort of discount (and you got NO discount whatsoever?). Whether that is enough of a discount for you, that is something that only you know

try another chain if its not in your price range too.

Finally, I'll add call the hotel and ask for any type of special rate that might help you out. You know what the best rate that you can get is, so if they can beat that, then you are in business