For now, the cost of my protein supplement isn't a very large issue (the money I used to spend on alcohol and cigarettes far outweigh the cost of my supplements), but I'm going to start studying at a university this fall, so then I'll have to consider the price of my shakes :)

My question is: aside from the ratio of protein to fat/carbs in protein blends versus isolates, are there any more factors I need to consider? I saw an ad for an 80% protein blend somewhere around half the price of the corresponding amount of 90% isolate, the additional 10% protein considered, and this could prove very economic if there's nothing more than the added fat and carbs to consider, which I am sure I can manage by some minor modifications in my meal plan.

Taste is no issue.