Good idea , but there are so many regional differences in price. Even a ball park average figure for someone in the North could be a lot cheaper than say we could get it in Cornwall. So we wouldn't know if we were being ripped off or not - except we would because Cornwall is always more expensive than anywhere else. They blame it on the extra transport costs!
If there's an horific difference on some parts we could always pool resources and some of us up 'ere could send them down to you lot down there.