I would not recommend doing that at all as it may put the SP in an awkward position and make it look like he is trying to barter the agreed price...and, depending on the lady, could get him shown the door, even if he has good intentions. Being upfront about what hes looking for in first communication makes it easier for the lady to decide whether or not she'd like to be put in that situation and is willing to offer only that service.
Generally when we speak of girls charging "extras" its frowned upon and if you're not upfront that your prices are the "minimum fee for just showing up" and that each menu item costs more you could be frowned upon more for pulling a bait and switch if men think that your minimum fee is your full fee. I dont want to sound mean but I would be very wary about advertising like that as it could bring you all sorts of headaches :-(