I've typically thought standard prices at AMPs were 400. But I occasional I see talk of 200 by others as if that were it. Have I missed a discount somewhere?

There is a bunch of AMP / spas in NYC that do not routinely offer GFE.  Their basic rate is lower.  Some girls on staff will offer GFE but at a higher rate and GFE is NOT available from everyone.  

There is also a bunch of 'higher end' places that I usually don't refer to as AMP because they have more of an indy or agency feel AND they are full GFE.  They command the higher rate.  

I have had some great experiences at the basic rate and some not so great experiences at the higher rate.  It kind of depends on what you're in the mood for and what your expectations are

Try silk tiger. $80 to the house, $140 for full service. nice place.