I hate to keep being Debbie Downer but I am confused as to why some of you don't seem to understand the current situation. As of right now, even if you got the chips for free, electricity for free, SB shipped the boards for FREE, you WOULD NOT make ROI. In fact if someone came up to me TODAY with a fully functional (as in 4.5GH with no hardware errors) K16 board and asked $80 for it - I would not buy it at this point.
Again -
https://docs.google.com/spreadsheet/ccc?key=0Ah7ZJVoobFY7dDRGQk1kdmJmaUJwZENKZUdNejJlWEE#gid=0Realistically if you start mining today, a K16 might produce 0.5BTC before it hits electricity/reward break point.
Well, what works for you, may not work for other people.
It's pretty much irrelevant at this point. Make whatever decision you're comfortable with, and stop trying to interpret what other people are doing.
Your spreadsheet, while quite nice, does not reflect certain realities.