25+ in stock, 10 minutes later "out of stock".
Who is spending over $1 per MHash/s right now on new mining equipment? That's never going to pay itself back at these difficulty levels.
Watercooled 6990's can push 830mhash/s per card easy, maybe even more if you cool the VRM. On a robust motherboard & PSU you can run 4 of these under Linux for 8 total GPU's = 3320 mhash/s per 1 rig.
Or, you could just buy 8 pieces of 6950's and need up to 2-4 power supplies, motherboards, CPU's, RAM sticks, casing, WLAN adapters etc. to run them. 5830's and 5850's are out of stock everywhere.
You can't just calculate $ per mhash.
You have to take in account the fact you need to build an entire system around the GPU, or multiple systems. A GPU doesn't run on it's own when you open the box.