Not sure how the extra supply for grapes affect retail prices of grapes for regular consumption. But at Costco in Southern CA, the price of grapes have been fairly stable (~$5.99 - $7.99) over the last year or a little more.
Did I just get lucky? Anyone else do this?
Vinifera makes a perfectly fine table grape and grape juice, depending on the varietal.
For example, Thompson Seedless, an incredibly common table grape, is vinifera.