My local Oxfam has an entire floor dedicated to vinyl and on balance I think their pricing seems fair, they can be too high on the rare stuff and there is no chance of picking up any classical wide band deccas for 50p any more, but I have still bought big ticket items from them (Tubby Hayes, William Russo etc.) as I wanted them. On the run of the mill stuff they can still be a few pounds over the typical online price but what you pay extra there you save on the exorbitant cost of postage of buying online. I think it's always nicer to be a able to find something you want in a shop so perhaps paying a premium for that is not a bad thing and ultimately it's all for a good cause.