Oh, I've noticed this too! When I was looking for my Trophese d'Venise grail, I'd find 'em on eBay but, for LOTS more than I could spend on 'em. I simply don't bid! Even tho I COVETED that scarf! Luckily for me, my very own Grail Scarf Fairy took extra good care of me, and that baby is getting worn, by me, any chance I get!
That being said, I'll still happily post whenever I'm looking for something--because I think you all are just THE BEST at finding Grails for folks! And if/when those bits I'm looking for pop up for crazy inflated prices on eBay...I just won't buy them. Sellers will get the idea! They'll bring the prices down!