I see a lot of these BFL single posts so I thought I would provide some input.
Buying used and having immediate delivery:
-$850 initial cash flow
(10BTC @ $11) = $110 x 12 months = $1320 total positive cash flow
Discount rate: ($1320-$850)/$850 = .55294 / 12 = .046078431 = 4.6078%
Net Present Value: $466.05
Internal Rate of Return: 7.520%
Projected 1-Year Profit: $470
Buying new and waiting two months for delivery:
-$600 initial cash flow
($0 x 2 months) + ($110 x 10 months) = $1100 total positive cash flow
Discount rate: ($1100-$600)/$600 = .8333 / 12 = .0694444 = 6.9444%
Net Present Value: $494.29
Internal Rate of Return: 8.844%
Projected 1-Year Profit: $500
$820 is the price at which the 1-year profits become the same ($500). Even then, the potential buyer must take into account the risk exposure he/she is subjecting themselves to.
Also, with the BFL SC products supposedly coming out next month, these things could potentially end up being worth hardly anything. Just my two cents.
LULZ! You are expecting to make $110/month? First of all, it's closer to about $104 assuming you aren't paying pool fees. But in case you forgot about difficulty, I'll remind you that there is no way you are going to be making $110, $104, or even $80 a month for 12 months. Oh.. and in case that wasn't enough, there's this other little thing called block reward halving which is currently expected in about 2.5 months.
Srsly, why are you trying to look at a 12 month window? There are too many unknowns after the ASICs hit and the reward half. Instead, lets focus on what I mentioned earlier, a 2 month window. You compare what a used Single can earn in the time you would wait for one from BFL, and add that to BFL's sticker price. That's the value of a used Single.
A Single can be bought from BFL for ~60BTC. Their recent shipping numbers have been seen as low as 40 days, but lets go with a 60 day shipping to be safe. Any used Single will make ~10BTC / month. Over the next 2 months, that's not going to change drastically. In about 3 months, that will (ASICs and Reward half).
Buying used (after 2 months)
-$850 initial cash flow
(10BTC @ $11) = $110/month x 2 months = $220 total positive cash flow
Projected cost of time after 2 months: $630Buying new (after 2 months)
-630 initial cash flow
(10BTC @ $11) = $110 x 0 months = $0 total positive cash flow
Projected 1-Year Profit: $630
