Just curious to hear some feedback from people that upgrade every refresh. I bought my 15" MBP on the early 2011 refresh, and I'm contemplating selling it to buy a new one on the refresh should it happen next week. For those of you that replace your machine each major refresh, what are you finding your average net expenditure to be? Net, of course, meaning, how much are you spending after you sell the old machine? My assumption is that people with base model machines make out a bit better than people with CTO higher end machines. I know Macs tend to depreciate slower than PCs, but what could you expect to sell a 1-1.5 year old MBP for? 75% of it's original price? 50%? 25%?