In terms of RTW there are a number of limited run or collaboration items that simply won't ever see a reduced price as they are in high demand. Then there are artisan items that are so specialized or hard to find that there's no way you can expect a discount once you do. Trust me, it's easy to find many OTR or RTW things that you won't find discounted. Now, if we're talking about used or thrifted items, I'll bow out, as I have next-to-no experience there.
That said, I have the majority of my purchases made for me these days, so I've also gotten away from the culture of getting a deal. The things I do find on sale are much more by chance and I have to talk myself into needing/wanting them (i.e. I wanted a patch-pocket navy blazer, but this besom-pocket blazer is pretty close, and a great deal). I rarely know exactly what I want and find it on sale in the same foul swoop. By settling I've found I just set myself up for failure as it's only a matter of time before I realize the "replacement" item just isn't exactly what I wanted.
If you're lucky enough to either not be that picky or to find exactly what you want on sale every time, then good on you. You're luckier than me. However, the culture of chasing a deal lends itself much more readily to frivolous expenditure and eventual buyers' remorse than a larger initial expenditure that addresses all expectations.