In hindsight, yes, this was the correct decision, but who would have thought BTC would go up ten fold in a few months? R1senfa17h' explanation is spot on in my opinion, this goes back to the fact, you should have bought BTC and not a miner, and you would be better off.

If you paid in cash for the miner, then at this point you most likely made your money back.

But looking back it's always easier to figure out what you should have done. You could have mined LTC starting in April and made much more than you ever will with any bitcoin miner in the near future for example.