Just a note, you put the cost field in at .25 USD, not .25 BTC. Should put the current value at $200 USD instead, which is the current mtgox price at .25 BTC.
ROI would be possible within a month if the difficulty never jumps more than 30% before February. So long as you keep it up even after it becomes non-profitable for you, yourself.
Tempting...
Thanks for the note.  Here is my rationale:
That calc is determining 
BTC ROI based on 
BTC invested and 
BTC returned.  There is 0 speculation in regards to 
BTC/$ exchange rate as I want 
BTC not $.  
I always set the USD/BTC value to 1.  Since there is no electric/hosting/cooling etc with this deal those calcs are accurate at 30% diff jumps for just under 30 days.
If you believe the 
BTC/USD price will jump and you are in $ then this is a good deal (based on my numbers) if you believe the diff at the end of January will be less than 1,994,380,572 then this may be a good deal.
The last two diff jumps have been ~15% and ScamFast clearly isn't shipping anything.  Based on that this could be a great deal.