I was in Ashkabad and Mary two weeks ago, no problems at all. The Grand Turkmen hotel is not the best, try the President, far better rooms. All payment for everything is in USD, ground handling reasonable but the ATC is good. All round not too bad, theres FAR worse places to go. Regarding the entry procedures, I'm on a UK passport and found it no bother at all, none of the 'suspicions' others have talked of. Second time I've been there and so far no big problems...........
For a CL-604 it was about $2500 cash.