My experience is that few are looking for that specific kit when you are trying to sell. So to entice the lookie loos in the buy sell trade section it has to be low enough to make it a good deal even with shipping. Then those who think they might build it in the future will take the bait. If a dealer sells a kit for 75$ and shipping is $10 and tax is $5 then the cost at your door is $90. For you to sell and ship (shipping will be $15 to $18 dollars), no tax 
. So to match, you would have to sell the kit itself for $72. Few will buy at a break-even cost because they really weren’t looking to buy that kit at that time. Just the nature of the beast. If you sold the kit plus shipping for $70 that might be enough temptation but that puts your kit sale price about $50. Your real decision is do you want the kit gone or to get back what you paid for it. When I sell a kit, I want it gone so I price it to sell and charge just a little over half the price for what it currently sells for. There is a guy in the Buy Sell Trade section selling a Tamiya F14 in 1/48th for $ 75, shipped. He wants it gone.
1/48 and 1/35 FS - Buy, Sell & Trade / Selling - KitMaker Network
Now I have a model shop that will buy my kits…but nowhere near what I want and will only give store credit and it can’t be used on a sale item. 
If he decides to retire I am SOL having store credit.