One machine is indeed profitable, but not for long.
If one machine is profitable, then so are 100. And vice versa.
That's why you need to go big,
Going big changes nothing (as an asic customer). Or almost nothing, I dont know what kind of volume discounts asic manufacturers give, but thats the only thing that changes. Actually, the opposite is true, if you go *really* big, you start competing with yourself. Theoretically 1 miner might be profitable, but under the same circumstances, 10000 may no longer be. If you cant see that, just calculate the ROI on 1 billion of whatever theoretically profitable miner.