You are not going to find anything at that price with a GPU worth using.
If you are willing to spend a little more talk to a bare metal supplier about installing you own GPU’s in one of their servers. My company did this and it was the cheapest way to get reasonable performance on a budget.
So what you're saying is I either self-host my machines or have to order >=$1000/mo machines with 4x 1080's SLI'd? There surely must be a solution to my very simple problem.