How can you mine 25(!) BTC with equipment worth ~500 USD within 1 month?! This is BAD advice!
What do you mean? I can just go out and buy parts from stores around my home. Worst case, I need to wait 2 days for shipment. Wtf 1 month?!About the recent babble of "Difficulty follows price!!!!!111" (+add some skewed excel-charts where 99% of data points are crammed in one corner to the mix):
Unfortunately this chart seems to be discontinued - I'll still link it as a warning though:
http://bitcoin.atspace.com/income.html
Please note the logarithmic scale!
If price increases as you say, you're better off cutting difficulty (+ noise + electricity costs + work hours + heat...) from the equation and just keeping BTC, as they will increase each difficulty increase anyways in value as well!
Mining would only pay off if you end up with more BTC by mining after some time. With current increases, it doesn't look like you will mine 25 BTC within the lifetime of a card that costs 25 BTC right now. Also you have to add constant costs like electricity + work to that equation!