Sellers who want a minimum of original RRP plus 10% for fees regardless, on everything they sell.. are imho, as unrealistic as Buyers expecting to snag a MIB figure, that regularly sells on eBay for £300+, with a 'best offer' of £30.. Let's not forget, secondary prices can go a long way down from RRP, as well as up.. eg. the usual 'very rare and collectible' description applied to a Hot Toys Tonto, or New Goblin figure.
Lets face it, virtually everything on eBay seems to be described as 'very rare and collectible' by some Sellers, ignoring the fact the Buyer may be looking at three pages of entries for the same item, many of which are much cheaper and in better condition.
I regularly see collectibles grossly overpriced by Sellers in the hope of snagging a noob, 'price no object' Buyer.. those figures get re-listed for 9 months, yet the Seller still acts all butt-hurt, if I have the temerity to offer a genuine market price as a best offer.. stuff that noise.
As others have said, collectibles are worth what a Buyer is willing to pay, if the Seller believes he can get more from another Buyer, fair enough.. but it is not the Buyer's job to shower every Seller with cash, particularly if the Seller has inflated the price.. because you can bet your bottom dollar, the Seller would be haggling for a better price, if the situation was reversed and that Seller was buying!
Imho, a good sale, is one where the Buyer is happy with the collectible plus the price paid, and the Seller is happy with the price received.