So in their minds, if someone paid ~24BTC today to buy a Single, and they received their miner in September, and let's say the USD price in September (when they receive their Single) of a bitcoin was down to $15 USD. Lets also say that because of this dramatic price drop that several thousands of people with ASIC and GPU miners left bitcoin mining therefore making the difficulty drop dramatically. So with the new price and difficulty, let's say it is possible for a person to make 48 BTC in 6 months. Would you concider it a wise investment? You originally paid 24 BTC and now within 6 months you have DOUBLED your BTC!! So originally you paid 24BTC (at the time worth 2400$) and in September-February you mined 48 BTC (at the time worth $720). But of course since these people don't care about exchange rates, THEY WIN!! right?
Really well-designed scenario that would satisfy the rules of a "good investment" by terms of BTC only which is being suggested above (which I did not create, not support the legitimacy of), while at the same time exemplifying one possible cause and effect relationship of BTC value due to exchange rate.
I agree with your overall assessment - and wish you the best of luck with this:
..and please don't knit pick about the specifics of this theoretical situation. This is not to argue what the price/difficulty/ of BTC will be in the future, or to speculate on BFL's shipping schedule. This is SPECIFICALLY designed...
Using the letters "BFL" historically opens the doors for all kinds of other goodies being injected to clearly-established hypothetical or theoretical scenarios
(Your example may be more of a hypothetical than theoretical, in this case, but that's probably just semantics)