It's difficult to always project difficulty out. When I project it out, I generally do the worst case scenario.
With 30% difficulty jumps, with 10% lower difficulty per jump, an early July delivery Neptune that has a total cost of 11000 USD @ 0.15kWh, will still be profitable in 2014 (although just barely), at a 750 Bitcoin valuation. These are not small jumps at all and I would consider it the worst case scenario (first jump is 400m, 450m, 500m, ect)
@Avenger, I do agree that buying and holding has been historically better. I believe most individuals that purchased various hardware in BTC would today have opted to buy and hold. Any Day 1 / Day 2 owners that can comment how much their units have generated to date in BTC? Let us know what device and average GH is as well. It is possible that you could have mined enough, and sold your coins and miners when it was at an ATH to earn 70k+ off a single miner. I think we're approaching that point where an original BTC investment may pay off. Of course, a year down the line, we may look at today very differently - that's what I love about this ride.
I have a day one jupiter (that was actually shipped on day one) that has already passed the BTC required to break even. If i was to sell the unit, i would be very much in the black. It was clearly a good investment from a BTC and Fiat standpoint
I also have a "day 1" Jupiter that arrived on Oct 7th. I also upgraded it to 6-modules and overclocked it to 1TH/s. The upgrade modules have already payed for themselves in terms of btc spent (5.8btc) and my uptime has been 99.99%. I mine on Eligius, slush's pool, and bitminter. I don't believe many have mined more btc than I have with a Jupiter and I've yet to break even in terms of btc (not that I'm complaining - I'm a very happy customer so far).
I don't believe you are in the black in terms of btc. What was your purchase date for your day 1 Jupiter and how many btc have you mined so far?