I suppose they may have a house wine brand, but don't recall seeing a house wine listed on menus...typically there'd be a bunch of choices but named vintners...like this pdf from Mama Melrose, scroll to bottom & you'll see wine choices, prices do vary. Fancier restaurants have fancier wine choices of course.
Do not recall a house brand even in Epcot or DTD and most of these are not Disney Owned..
The prices at Disney for Wine are within reason--one glass would be about what you could buy the bottle for
in NY expect to pay almost twice that