For me, it's about defeating the difficulty so I continue to make what I'm making now.  Buying two allows me to defeat the difficulty increase and add to my profits until next increase.  If BTC value goes up, I make even more and payback shortens a bit.  At $833 BTC, these are only $44.15, still $14.15 more than I wanted to pay, but I'll take the hit just to defeat this next rise and add a few more nuggets.