That's not necessarily true. My takings are already at 81% of my expense, and I'm only doing it for 6 weeks. I gradually built up my rigs so average is like 50% for the 6 weeks and still I'm at 81%. It could be 100% allready if not for mtgox...
So resell does not matter for me. If I don't need them anymore then I sell them at a price they buy it. It's a bonus.
I don't see how another avenue to profit negates what I was saying. Fact remains that a new GPU sold at say 75% of purchase price vs an older GPU sold at 25% represents a big chunk of much higher confidence ROI in a speculative market like mining. This is specifically true when you're getting into the game this late. Personally, I have no intention of buying more GPUs for mining - I stopped at the end of January.
Resell might not matter to you, but that doesn't mean it doesn't matter... and if you're doing ROI math as precisely as you are, it makes no sense to consider equipment resale a 'bonus'. At least that's my take.