But my early Bitfury, ASICMiner, KNC, Bitmain and even BFL miners were very, very profitable.
uhh what? sorry but what means profitable for you? ONLY reason why you had profit on those machine is, that BTC price spiked and you had those devices in hand.
Anyway, you ROI you USD but not BTC my dear. or you mined more BTC than you paif ro HW? I don't think so. (and yes, I had 4x Jupiter, few blades and few BFL cubes, before you ask me - and believe or not, it was much better to melt USD to BTC and hold them than pay for HW with them..paying 0.2USD/kW)
I stated clearly that my success was due to "the phenomenal rise in BTC price."
I believe I only paid cash/credit for the BFL Little Single (which I resold for massive profit), some ASICMiner Blades (and USB sticks) and my initial KNC preorder. All of the following gear; Bitfury (+2THs), 3 BFL 60GHs Singles (lol), KNC FrankenJupiter plus extra modules (~4.5THs), assorted Bitmain miners (3THs), Spondoolies (~3THs), 2 Monarchs (1.5THs) was bought with earned BTC. I never resold any other gear except for the Little Single.
I still hold a nice little chunk of earned BTC despite making sizable purchases on NewEgg and TigerDirect with BTC and exchanging many BTC to pay bills for several months while my business was transitioning and my income was nil.
I can safely say that I had a very positive ROI... USD and BTC. And not because I made spectacular decisions. It was simply because I bought a large amount of mining gear when the BTC price was extrordinarily high.