I read your blogpost.
I think you & I are probably from a different time and as such consider charity shops as something different from what they are today.
W'n I were t'lad the charity shop is where you bought dead men's jumpers for 50p so that you had a warm jumper. You could buy jeans and jackets there too. They took EVERYTHING in and all the coats were £2, Jumpers 50p, Jeans were £1, as were trousers, and paperback books were 25p each or 5 for a pound. Hard back books were generally a quid each, but they didn't get many of them. The reality was that many a house-mum clothed her kids, and maybe herself/husband in these bargain clothes. No-one would know but thats what charity shops were for. Sure, they allowed the people in the detached houses to empty their closets and feel good about themselves. It also helped them know who to judge when in Sainsburys as they were wearing YOUR blouse that had that little 'nick' that no-one would notice except you.
I think in the last 10-15 years the tide has changed and now they are places where a commercial enterprise sells you items for just less than RRP (or more if they think they can get away with it) where the people who used to give away stuff now occasionally go to BUY things so they get a warm feeling inside about helping people out by 'buying' clothes which hopefully no-one down the rotary club donated!
The fact Charity shops DO charge so much means that if you buy something, you can do what you like with it. Of course, not all charity shops are looking to get the most £££ for an item but they do sell items for what they are worth ... to them. If you see something for 50p and can sell it for £50 on ebay then so what? If you want, tell them they can get more for it online. Most wont care. If you feel REALLY bad just donate a load of items for them to sell or make a donation to the charity shop of your choice, if it makes you feel better.
When I lived in Victoria there was a charity shop down the road which always had designer brands in. But they were priced pretty heavy. I saw a peice of pottery that my mum likes and went to enquire the price. They were selling it for £20 MORE than I could buy one delivered from ebay (£40 total!). But someone will buy it, or they'll reduce it.
No charity shop is going to go bankrupt because you made a profit on something you bought from them, thats for sure.
The Reverend