I'm sure you are right about the prices, after all business is business and a lot of work goes into a good cab.
When people ask how much for my custom cabs, like a "unit price" - I don't like to give a number at all anymore, unless they're actually on sale (they're not). Each is bespoke and unique, they aren't slabs of beer.
If they still push on for a number, I might say something like "depends on the cab, they're all different, but definitely more than $4k". People aren't shocked when you put it like that.