I can't speak about the price discrimination in the fitness industry, but having experience in the Hotel industry I can say that this a very difficult situation to be in. On one hand, you have a product that is perishable in the fact that if you don't sell it (the room in my situation, or in this case the space in the fitness area), you can never sell it again; So in certain situations you will have to sell at any cost, or lose that potential gross profit. In theory, all is well until you have two people checking in at the same time, and customer A is paying 30% less than regular rate while customer B is paying the regular rate. In the case of people checking in together as a group, and checking into the same type of room, its always best to ensure that there is a common rate because obviously those people will talk and no one wants the short end of the stick.

In dealing with the situation, I think there are a few things one can do as the seller. You can simply budge, and go for the lower rate. But you wouldn't be very good at sales if you did that. Instead, what I often do is look at the emotions of the individual and you can normally tell how to handle the situation. In the hotelier industry, when a rate discrepancy occurs I usually state that you must book through a different distribution channel to attain the rate that the individual is arguing for. I go on to state the channel they used, and explain that the package/rate is no longer available, but what I can do for them is give them the special managers rate which is a 5% discount (or adjust until satisfied). This lets the customer feel like they are winning, all the while keeping your rate integrity. Another way you could handle the situation is stating that they are receiving rate X and that the rate at the current time is actually 10-15% higher than their current rate, and most people are okay with this, believe it or not. In the end, you have to either give the user some sort of value (such as a complimentary upgrade if there is a better room vacant and its late at night) or budge just a little. Otherwise you will have a bitter customer, and they will never be pleased nor will they ever return. In the end, how the customer is acting emotionally really determines how much you should give up, but you should always give up just a little and then add a little extra value - I believe this practice can be transferred to the sale of any product or service.

On the other hand, I have experienced very irate customers who act like total assholes, and they just end up with a higher rates. Don't be that guy.