Everyone has a different argument, but at the end of the day it really should boil down to ROI.
And compared to other investments in the world, 6 months to make all your money back (and potentially a lot more if you hold your BTC), is a pretty good investment if you ask me.
Stupid, even if you somehow, get ROI in 6 months, you will have negative cash flow after that. Do you know what that means? (since you seems to understand ...... investments and all)
And if you count on BTC price, then buying BTC now with it in your hand.... you wont lose opportunity in case BTC price jumps in less than 6 months.
However, all of these is moot because you WILL NOT have ROI with S4s. We're talking about ROI btc here.