Trust me, I know the feeling from dealing with a dealer. I recently tried to 'move on' my collection of US/European H0 trains - mostly unused [ever] and still in their dealer-sealed boxes. Four sets of twelve passenger cars for various named trains in the USA and Europe, matching locos, a collection of brass cabooses and some rare Great Northern stuff, Total value approaching £6000.
After a bit of bottom-lip chewing and farting around on his Blackcurrant, he offered me just over £600.
Three of the locos alone cost just under £2000....
tac