...and what criteria determines the amount? I feel that one major factor is the law of supply and demand. However, on another board, the majority of hobbyists feel that rates for visiting providers should be adjusted based on the cost of living in a particular area that is being visited. An example would be, if a bottle of beer could be bought in City A for $4, while at City B beer is sold at $9 a bottle, if a provider who's rates are $300hr in City B should drop her rates to $132hr to match the 44% difference in the cost of living between City A and City B.
I saw on the board recently that a provider stated potential interest in visiting the area in the near future, and a hobbyist responded by stating that she needs to look at what the local providers rates are and adjust her rates accordingly.
I understand that the area is more sparsely populated and that the client base may not have the number of higher-end clientele that a major metro area will have. That's an easily understood fact. But the presence of that fact has now seemed to have given those local to the general area the initiative to stand up and declare that all visiting providers need to adjust their rates because of it.  

I could understand if that $132 the provider made in City A magically transformed into $300 once she entered the city limits of City B to adjust for the cost-of-living difference. But since we know that doesn't happen it seems to me that telling a provider that she needs to adjust her rates so more guys can see her when she comes to visit could be seen as, well, tacky.
I'm not assuming that providers don't make adjustments when touring. But like I said, it has always seemed to me that it has been more of a supply-and-demand thing than a cost-of-living in a particular location thing. Other opinions??