Aren't addressing the large buy-in cost that exists now, will increase past the point of Moore's law soon, and also that this was not the case for the past 2 years.
Yes it was. Before GPU mining came along, in order to increase your hashing power, you had to buy more CPUs, which meant an additional mobo/PSU/memory/etc. And back then top of the line Core i7s were (still are) more expensive than 6990s... yet people still did it.