The problem with your argument is that the reason you were able to ROI is because the price of bitcoin increased. If instead of spending $1,300 on a BFL miner, you instead bought $1,300 worth of bitcoin your investment would be worth well into the six figure range today.
Actually it would be worth $5,200 (1300/100 = 13 BTC). Yes, a way better return (and had I known I would have done things differently), but I paid in dollars, not BTC, which would have been even worse from an ROI perspective. (5 BTC returned on 13 BTC invested, ouch!)
In fact, it would appear that it is not profitable to buy mining equipment using BTC at all anymore, since no miner will be able to recoup the amount of BTC it would cost given current price and network growth, no?
Buying in april would also mean buying at the end of a large price spike. If you had purchased even a few weeks (or a month or two) earlier then you could have purchased a lot more (with BTC=20 you would have purchased 65 BTC = ~29k today, with BTC=13 you would have purchased 100 BTC = ~43k today).
Even though you paid in fiat for the machine you could have used that fiat to buy bitcoin