I take Puppet's spreadsheet to be a simple demonstration tool, I don't think his intention is to imply it's an accurate model. I would say his assumptions are much more sound than your main premise though. If even with free electricity a miner cannot recover their capital cost, NO ONE WILL BUY MINING EQUIPMENT. Sorry for the caps, but this keeps on coming up and it's a fundamental logic flaw. With free electricity your costs of running equipment are negligible. To say that the capital costs will never be recovered assumes that income approaches 0 as the network hashrate approaches infinity.
Answer one simple question, with the assumption that continued increases in difficulty will mean that even people with free electricity can't recovery their capital costs in equipment, who do you think will be buying the ~250PH/s worth of mining hardware necessary to even double the current hashrate?
People who can get the mining equipment a lot cheaper than it is normally priced for the "consumer". That is, people placing gigantic bulk orders, people with exclusive partnerships with manufacturers, and the manufacturers themselves.