I'd like to say in my defence I'm not because some known skin irritants seem to exist aplenty in very cheap products; but I avoid those expensive brands that have them too. I echo the sentiment time and time expressed in this thread that I have better luck paying for something I know will work and helps me achieve the look I'm after, rather than getting a cheaper item only to discover it just doesn't cut it.
Someone mentioned that Dove and N'gena works just as well as high-end for them, but for me, it could mean insufferable skin irritation, where I feel like my skin is burning. Yes, found out by trying it too.
I have however found some fantastic drugstore-type items that I considered to be fantastic; a shame that it just seems to be harder to find such items otherwise, wouldn't we all be flocking to get them? I confess that I wouldn't buy so much MAC if I couldn't get it cheaper - as seems to be the case on say, eBay. I'd pay full-price but if I did all the time, would have a much smaller collection.