After silently browsing this forum for years I finally found something I couldn't read anywhere here

I'm an Emerald Club member, but I've always wondered how it works - I can pick up any car from the Emerald Club aisle, and then drive away in it, but how much do I pay for the car?

Is it dependent on the reservation I made using Emerald Club? The size/class/model of the car?

How do I know that I won't pick up a car that will cost me more, than I'm interested in paying?

Thank you for the help in advance.