This scam and other versions of it are aimed at solo male travellers in IST and elsewhere. It's a very expensive scam in IST. Name dropping with the police in advance of the return visit with the police to challenge the set-up has yielded positive results before.
Generally, don't let a stranger (i.e., "newfound acquaintance") have their first, second or third choice of time and place; make your own suggestion and don't be led.
Someone should also notify the immigration authorities.
