I'm not sure I agree with the statement about charity shops being 'dual purpose' - weren't they always there to make money for the charity rather than providing a service to the poor? That was just a benefit.
However I do totally agree that the prices in charity shops have become ridiculous - we have quite a few in the small town I work in and love nothing more than a lunchtime rummage. One or two here are starting to price themselves out of the market.
Our British Heart Foundation is the best of the bunch by far - really really nice clothes (which I've bought many many of) at reasonable prices. Note I said 'reasonable' not bargain. I paid £25 for a fantastic 3 piece suit with a matching tie. It was only Debenhams, nothing high-end but would have been pricey - it was worth every penny of that £25. Similarly Jack Wills shorts for £6.50 - great condition and a nice cut, worth the money. The Scope next door though... everything is mega bucks, whatever the label and condition. Most of it is generic supermarket stuff or ancient outdated things anyway. I think I've bought on thing from them; a leather French Connection belt which was, to be fair, worth the £8.00.
The manager at the BHF told me she turns her stock round ultra fast and prices at the upper end of what sells. I think this is the best way to do it - a shop I go into most days because it's fresh stock and prices that I can't say no to! A good technique.
Putting on eBay prices won't shift stock quickly - after all the whole bloody world can see an eBay auction, so a bigger audience! With the case of my suit, I may well have been the only 5'8 man with a 28" inside leg who wanted a charcoal pinstripe suit in the whole of my town! Had it been the £50 or £60 it would probably make on eBay, I wouldn't have bought it and I bet no one else would have either. Price to your market charity shops!