With Avalon, ASICMiner, and BFL units shipping and the difficulty skyrocketing, it's possible that if you buy a mars unit from kncminer you may never pay it off and break even, let alone make any profit.
There must be something I'm missing or not understanding, so please forgive my ignorance. Don't take this as an attack on kncminer - they claim to be working on ASICs as well as releasing this FPGA unit, but I'm just curious as why they aren't focusing 100% on ASICs.
I think the reason why they are producing an ASIC design first is because they are using the OpenCores route to ASIC development. Once they have the software running on the FPGA, they can make identical (except faster) ASICs.