I've read through many of the newbie postings and haven't been able to find an answer, so I apologize in advance for thsoe bored with this question.

I've hobbied in AMPs for a few years now and negotiations have been easily handled.  For the most part prices are in a common range of expectation.

Recently I tried and Outcall service with a company in Vancouver.  I wish I'd known of this site before so I could tell the rest of you to stay away.  The girl on the phone sounded very cute and I told her what I was looking for and she suggested a couple girls.  I selected one, and we set a time.  About 15 minutes late I get a phone call from a girl other than the one I was expecting and she said she was stuck in traffic and would be there in 15 minutes.  30 minutes later i get a knock at the door and the girl standing in the doorway is not even what I'd described.  Her hair was still wet and dressd in very unbecoming clothes.  I had misgivings straight away.  I was told by the service to have $200 waiting which I did.  I was also told there would be no other donations required with the caveat that anything else was between consenting adults.

In any event, before the festivities begin she informs me of her rates.  Way more than I was prepared to spend on the girl I was hoping for much less the mutt in front of me.  I politely told her this was not what I was expecting and I asked her to leave.

I realize providers have donations for periods of time.  A gratuity I have no problem with for GFE, but is 100-200% the norm?

Sounds like an agency where you pay for the "agency fee" before the discussion and for the service afterwards.   These are impossible situations for the client because you have already invested time and money--and expectation--into the enterprise before the price is negotiated.   Better to stay away from such adventures and limit yourself to providers with good reviews on TER.   That is what TER is for.