First off let me say I agree with the girls posting here. There's a wide variety on this site with varying prices so there really is no need for a guy to call up bargaining and bartering with an escort.
What I will say is that in this country there has always been a tendency to haggle for a bargain among consumers, particularly pre-Celtic tiger when a higher proportion of goods / services were were family owned as opposed to the likes of McDonalds, Boots, Foot Locker etc. This all but disappeared in recent years and obviously you wouldn't have ever do it in a restaurant (or with an escort!) Anyways... the point i'm making is i don't think it's any surprise to see it re-emerging given, well, everything that's going on though haggling with an escort is a step too far.