As a brand new seller, I've also found pricing to be somewhat of a challenge, as well, Terrasita. Truth be told, sometimes I don't feel "qualified/deserving of" setting a higher price. I think that's just part of being new at something, and I already, in the short time I've been in business, feel more self-assured and more "deserving" of charging more for what I truly know to be a quality, desirable item. Does that make sense?
As for setting the price, well, on the one hand, it's perfectly obvious: I can't price the majority of my items the way a seasoned professional with stellar stock can, for the simple reason that I do not have the same stellar stock! Never mind the traffic and all that... my adorable little wiggle dress just isn't a highly desired Vionnet in perfect condition!
That said, it's also important (IMHO) not to be the rat fink who "undercuts" my colleagues -- selling something that IS on a par with their offerings at an absurdly low price. I might price one of my items far lower than they would (successfully) dare, but I won't price it so low as to undercut.
I use the following guidelines for pricing my items:
1. How much did it cost me?
2. How much time and effort went toward rehabilitating/cleaning/photographing, etc.? How much your own time is worth is a personal question. I tend to undervalue my vintage time, compared with, say, what I'd earn doing medical writing. But if I didn't, the hours would send the prices over-the-top!
3. How much are truly comparable items being sold for (not just offered for, but SOLD for)? I've found most sellers are willing to share their sales prices with you if you explain that you are trying to set a reasonable price for a similar item. Many will explain how they determined their own asking price, which can be very helpful.
4. What would YOU pay for the item without feeling you were "getting the greatest deal of your life" or "being completely ripped off?" Somewhere between the two seems like the perfect price.
In short, I price the items so that I, as a consumer, would feel comfortable paying that amount, while I, the business owner, don't feel I'm taking advantage of customers or giving stuff away and undercutting my colleagues.
When I've asked colleague-friends privately for help with pricing, they nearly always agree with my "gut reaction" price. So I think my crazy "formula" is working most, if not all, of the time.
As far as "finding your niche," I completely agree with what the other posters have written. For me, that does not mean aspiring to being another ultra-high-end seller. There are several of those out there (some of whom I count as friends) and they do a fabulous job at it. It's their niche. I link to them from my own site because I respect and trust them, and certainly want them to continue doing well. And frankly, I don't see them as competition as much as "inspiration."
But you have to go with what and who you are. I've never been a label-conscious person. If I like it I like it, if I don't I don't. The name on the label doesn't change my opinion. Given that, I don't think it would be appropriate for my focus to be "designer/high-end/label name" because it wouldn't be true to who I am. I'm more about fun and affordability.
I am, however, in the position of being able to sell vintage without it being my sole means of paying the mortgage or feeding my children. And of course that takes a lot of the pressure off and allows me to do what I like without worrying about the money, per se. No, I don't want my business to fail, and yes, I have dedicated thousands of hours and not a few tears to it. And no, I cannot afford to lose money over the long run. But knowing I will be OK if it doesn't work out immediately, or sales become slow for a time, is an enormous luxury which, I recognize, is not the case for many sellers.