The answer depends on whether you mean the fastest consumer ssd or business enterprise ssd.
The fastest are enterprise ssd's. Prices for the really fast enterprise ssd's designed to do specific tasks start at about $1,600.00 USD and go up into tens of thousands of dollars.
The world's fastest single consumer ssd is currently the Samsung SP951 M.2 PCIe 3.0x4 ssd. The SP951 should be available to consumers at the end of next month.
I maintain an ssd database listed in a sticky at the very top of this forum section. Here is the link:
How about 12GB/s and 650K IOPS -- NetApp -- probably more than your budget... The fastest ssd "in the world" don't fit into anything smaller than a rack...