Exactly. Models have very little inherent value. They are only worth what somebody is willing to pay. NOBODY CAN TELL YOU EXACTLY WHAT A KIT IS WORTH BECAUSE NOBODY KNOWS!! It changes every minute.
If you are selling rare, older, sought after kits (the first two don't always mean the last), then there is no bigger audience than eBay. Plain and simple. More buyers equals a higher price. There is absolutely no venue that can come close to eBay's magnitude. Love or not, that's the way it is.
Fees? You bet. About 10% from ebay and PayPal. But I guarantee you will lose more than 10% selling them any other way - be it CL, as a lot, or even setting up your own website.
If you have easily available kits - your best bet is as a lot.