We just sold the last of our seedless grapes at the Amish Produce Auction, 5 varieties including Concord Seedless, Jupiter, Marquis, Canadice and Reliance. They were about 10# to the box, and the highest selling box brought $19. They averaged about $16.25 per box. The box cost $.90 so that brings it down to $15.35, over $1.50 per pound. I'm happy with that!
Haven't sold any wine grapes there, but probably will as they come on. We'll see how they do!
The reason I'm posting it is that I know several of you with vineyards live within an hour or two of a similar Auction. You might give them a try.
Good Luck!