It is all about demand.
If no-one wants an item the price stays low to try and re-coop the cost of making it, if you have a huge number of people who want the product "just to be just like that bloke on telly" then the cost goes up and doubly so if the product is made to the specs of the name of the telly guy. (In part to reduce demand so the maker can actually produce all of the orders and in part 'cos he has to make money on what the maker charged)
This is why companies get tv/film stars to promote their product, to increase sales.
The quality could be the mutts nuts or worth less than the invoice paper it is printed on, but, people will pay what they perceive to be value for money.
I would like a RM badged knife, I like him and his media output, but I am not going to buy at the inflated price due to "wannabe" causes, first hand or second hand just as I will not buy from Gerber due to their use of a certain person as a sales ploy.
I do not buy into any of it.
Plenty of good, honest, skilled and bushcraft minded knife makers out there who could make a bespoke knife for you for less than a second hand RM type.
Rob.