My DH is a trustee of a local charity who have a number of charity shops across the area.
A few years ago they decided to go a bit more upmarket with their shops and branding - refitted the shops, etc. they rebranded their furniture shop as vintage/shabby chic and pretty much doubled their prices.
In that time profits have significantly decreased year on year, the shops have much lower footfall and they're now looking to close some of the shops as they're just not paying their way. Before all the refits and rebranding they were doing well. DH says its like banging his head against a brick wall - yes, they have to maximise their profits but he can't see the sense of high priced stock hanging around for months rather than having lower priced stock selling quickly
On asking locals, everyone says the prices are way too high, they don't want fancy shops with matching coat hangers, they want good quality, second hand goods at reasonable prices. Stock hangs around (because it's too expensive so people aren't buying it) so people don't bother to go in very often as it's the same stuff for sale. Donations have dropped as well
Looking at the Oxfam, BHF, etc shops around here and they all seem to be suffering the same way
On the other hand, a friend is involved in an animal shelter charity with a couple of shops who have stuck to their tried and tested formula of cheap as possible over the years and the place is packed, profits are increasing, donations are up and they're looking to expand
It obviously depends on the area, but here, yes, the bigger names who charge the higher prices all seem to be losing out to the little independents with their lower prices