The wave is just breaking over here. Worst possible time to sell your collectibles as you'll get less for them, as less money in most budgets will be allocated for luxuries.
The grails have enough demand for them to ride the crest, for the moment.
It's one collection, so I do not wish to sell any. As is always the case, there are at least three sides to any coin. You could sell off the lesser items, at a loss, but not care. You could sell off the grails, knowing you will have gotten the best possible price, and be happy with that, also knowing you might never possess one again, or you could sell off your unwanteds, being happy to clean up your display, along with a grail or two, to get some liquid funds, and be happy regaining some space.
I don't usually sell any items, so I can't say which grail figure I have owned, that I've sold, and wished I hadn't. I'll participate by using my own interpretation of your question.
You're best to keep your favourite pieces. These will hold off the pangs for having sold off, perhaps, a more rarer piece. My favourite 1/6th figure is the Enterbay Bruce Lee Enter the Dragon 'B' version. My favourite PF is Universal Monsters The Creature from the Black Lagoon.