It's true what Rosee says, that with shoes you often have to pay full price or your size will have gone. This is also true for smaller sizes of clothing, so I find myself paying full price most of the time. Every now and then I'll get a good deal, but mostly, if it fits and flatters and I really like it, I just buy it. Like Louise, I simply don't shop in stores I can't afford!
The other bonus of paying full price is that you get to wear the item in the season it came out, so you feel like you're part of a trend at the start, as opposed to getting on the bandwagon a season late. I understand that "trendy" is not a word most people view positively, but hear me out. It's true that I would prefer to be labeled "stylish" rather than "trendy" myself, but I suppose I do follow trends, at least to a degree. I don't jump on a bandwagon if the trend doesn't suit my figure or my personality, but if it does, I'd rather get on at the front end than be trailing behind by a season or two. If you at least somewhat keep up with trends, I believe it makes you seem more stylish. Or, at least, it's one component of style.
So, when you ask if you should have bought your thrift store blouse new and enjoyed it for several years, rather than buying it late, I would have to say yes, you should have (providing it was in your price range). But, did you see it new in the stores several years ago? Maybe not. And, if it's so over-the-top gorgeous, it's still great that you snagged it, even if it's late. Better late than never!