Just to throw it out there... that $1 per KH/s must also include your supporting infrastructure as you mentioned... mobo, RAM, CPU/HSF, HDD/SSD/USB depending on how you are running them, PCIe extensions, the 1200-1600W PSU you need to run 4+ cards if you are doing so and all the extra connectors you need to run cards that require more than a single 6 pin PCIe power connection.

A single 800+ KH/s GPU running $500 - $750 still needs $100+ just for a basic mobo/CPU/RAM/BOOTDISK/PSU and that's cheaping out... you can easily reach +$200 for a base PC to run the GPU... and more if you want to run a multi GPU rig.

Tell me where I can get an 800 KH/s rig for $400 ($.5 per KH/s) and I will delete this post.

Hell the highest noted GPU on the scrypt litecoin comparison wiki is the Sapphire Tri-X 290X at 1002 KH/s and that's on Newegg for $750 right now and is noted running at 385W. A new setup could easily run $1000 to get that 1 MH/s running stable, whereas $1000 will buy you 3 gridseeds, a Pi, PSU, barrel jack connectors, a powered USB hub and some sort of case to put it all in, gives you a MINIMUM 1150 KH/s AND only runs a total of ~30-35W max in scrypt mode including hub and Pi. Compare the GPU rig running ~500W total to a 35W 3X gridseed/Pi and still get 15% more hashrate for 1/14th of the power cost... and probably still have funds left over. For $.10 per kWh that is ~$400 a year less in cost of power. So while you may be able to resell that GPU for $400+ next year... that only brings you to break even with the gridseed setup... before the extra 15% hashrate is included.