I can echo what Jerboa has said as I have fallen prey to this myself in the past. One example, there was a very pretty red haired girl called Verity who used to be listed through Hamiltons / Bijoux or Allure for £300 / £350 for quite some time. She looked very tempting even at these crazy prices, but luckily I never booked her through them. Last year I found her on AW for £250 and took the opportunity (still expensive) and no shortage of services provided there either. I was lucky here, but in other previous cases I have only later realized that the girl I have seen has been listed cheaper elsewhere on another site / AW.
All you have to do is read the thread "slow at the minute or just me" on saafe, which has been running almost daily since 2008, to get a sense of just how bad business is for these ladies.
Some other live examples I have come across recently (not visited any of them though):
listed here at £200 p/h, whereas she is listed here at £300 http://www.agencybarracuda.co.uk/escort/amanda-2/
. (I have even messaged this lady to see what services she is happy to provide and it is no different to what is stated in barracuda).
listed here at £350 p/h, whereas she is though listed here at £160 https://www.adultwork.com/2092228
listed here at £500 p/h, whereas she is listed here at £200 https://www.adultwork.com/1294978
listed here at £600 p/h, whereas she resembles this profile at £150 http://www.hot-collection.co.uk/escort/victoria
If they are doing so well charging a higher rate, why do they have another profile charging cheaper rates?
The only high end type agencies I would recommend are Maxes, Bijoux, Hamiltons and Allure.