What do you mean by " wine in a box is classy "?

It's a 'Sarcastic' way to tell you the wine is cheap as all of them are when in boxes-milk carton-like.

I think it's ironic because it blatantly isn't.

I buy a 5 liter box every week for $15 and I love it. Who's laughing now? The man who buys cheap wine and enjoys it or the man who buys expensive wine but always saves it "for best" and never drinks it?

Slapping the bag is classy!

I mean that wine in a bag isn't.

Every thing is fine until you use it.