There can be some truth to that.
I have a few providers that are in the $200 range, GFE and eye candy to boot. They are part of my "private stock"
My ATF was a $200 AMP girl that was awesome.  
However, many providers in that price range are not GFE.

I also don't see much of a difference between a $300 provider and a $500 provider as far as performance is concerned.  

It is all about economics 101; sometimes called supply and demand.  In the current economic times, sometimes the threshold for descretionary income is lower than say 2 years ago.  

Also, some ladies charge more because they really want to stay low volume.

I agree to a point.  I'm not going to spend $1000 to see a lady when I can get 3 one hour dates for the same amount of money.

A G sounds really high but if it's late at night some with more money would go for it.  Personally, I don't have that kind of cash...  $200 is about minimum, at least around here.  Ads for less are one pop, shorter time, or something.  
It takes some research to find good providers but those I find become Favorites.  Yes, I can get a bunch of GFE sessions for that G.
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