I would suggest possibly typing the name of the kit in ebay, and there is a way to search finished sales to give you an idea. It really varies day to day kit to kit on values. Some things have held a lot of value others not.

With the low amount of builders left. I am surprised some kits are as high as they are. I am not sure if there are still a lot of people just collecting them, that don't plan on building..

Good luck though , sorry to hear you lost your Pop.....