This is a great question, and one I'm also struggling with. In the past, I never waited for sales because if I did my size would be long gone. I've been burnt way too many times. Even now, when I see items that I bought full price that are at rock-bottom prices, and still in my size, I don't have any reservations because I've enjoyed several months of wear already. (I'm only tempted by the thought of duplicating!)
More and more lately I do stop myself and think, "It'll go on sale soon and the economy is so slow, my size will be there, so hold off." And I do. I am tracking a handful of things.
I guess I would say this: if it's an investment item that will get years and years of use, it may be worth the full price. I wouldn't spend full price on knitwear or sweaters, they wear out too fast and need constant replacement. But I *might* pay full price for the absolute, most perfect black leather moto jacket. I didn't find one last season. I am very picky, but it's also the size factor. YOu want such a jacket to be form-fitting and hit just right; if it has zippers on the sleeves it can't be altered; this is not as easy as it sounds when you're my height. Now add into that I want one that is a nice quality leather.... it gets really difficult. I'm not about to pay $1358 for one, but I *might* part with as much as $500 for exactly the right one. Because it's something that I'll get use out of for years and years.
The other item in this category for me would be the perfect, classic trench coat in just the right white (probably cream for me). This is proving to be very difficult to find. I want one that is waterproof and preferably with a zip-out liner, so I can wear it in colder weather too. So I might pay full price for something like this.
Waistcoat? I dunno. Angie may disagree with me, but I fear that this is more of a trendy piece. Vests come in and out of style. I remember wearing them in preschool (okay I don't remember, but I've seen the pics of the cute outfits my mom dressed us up in), then in high school, then again in my early career. Then not again until recently. So I fear this is one of those items that is fun to wear now, but will go out of style and not come back in style again for a decade. And I will probably be heavier in a decade. So my strategy with vests is to buy low-priced. I only have one so far. I actually don't wear it that much. Not as much as I would a leather jacket or trench coat.
I would pay full price if I found the perfect chesnut boots (I'm still looking... scouring the sales racks lately!). The good thing with shoes is that you don't change sizes that dramatically over time.
Jewelry ... no, I have my best luck shopping the jewelry section when there's a sale on. I think it's because the lower prices mean I am more willing to experiment and take a risk.
I would also pay full price for upgraded denim clamdiggers that fit as well as my cheap ones (which will probably only last me one more summer, sad face). And a denim skirt that didn't make me look all goofy, like I have a huge pot belly. And maybe a perfect red wool pencil skirt, which has been on my wishlist forever.
Okay - do you see my trend here?? I would happily pay full price for the items on my wishlist, provided they fit well and were truly fulfilling my wish in every way I'd envisioned - not just a "close enough." Everything else? I will hold out for the sales instead!!!