I always say there isn't a fuck in the world worth more than £150 ph. Other people will have a different number, but pretty much everyone has a breaking point somewhere.
But prices aren't generally the issue - there are always going to be girls charging more than you're prepared to pay, so you just don't see those ones. The issue is what you're raising here, the rate at which prices are increasing.
Rebranding and doubling the charges is taking the piss, but it's not an uncommon thing at the moment. Loads of independent girls have taken it upon themselves to start charging 50% more than they were a year or so ago - often with more extra charges than ever, effectively doubling their rates. And really it only comes down to their greed and a false sense of worth.
Then it flows down to the ones who were sensibly priced seeing the prices others are charging and boosting their own to match.
That breaking point I mentioned? There are loads of guys on here who are still prepared to pay the prices being asked, and as much as there will always be girls charging more than you're prepared to pay, there will also always be guys who are prepared to pay those amounts. But it still boils down to supply and demand - at some point the customer side of the industry as a collective will reach a breaking point for the majority and things will either have to change or it could see the beginning of the end for the oldest industry in existence.
But as has been said on many an occasion, threads like this won't change anything. We just have to vote with our feet and the demand side of things will gradually disappear.