when i go looking for bags, whether it be at saks or or the gap, i try to focus not on price, but on whether a bag "looks expensive." not in the way that i want others to think that i paid a lot, but in the way that if a bag looks expensive to me, it's going to have quality stitching, no loose threads, excellent material, a nice lining, and beautiful, innovative design. there are plenty of cheap bags that look expensive and expensive bags that look cheap, at least to me.
price is a measure of perceived, not actual, value. a company's marketing department does a lot more thinking and studying and researching about a bag's particular price point than we will ever know, and they work hard to make the bags' percieved value high. that's why a sense of personal style becomes so important when it comes to this kind of thing, because if you don't know what you like, you're just their puppet.
so to answer the real question, i'd be willing to pay more for most of my bags than what i originally paid for them because i'm picky. i use what i buy and i don't waste. i think long and hard and usually wait at least a week before i buy something that i see and like. i do a lot of research.