They do have some cheap-esque champagne but chances are extremely high they will run out. I've been told by several FAs they only stock 3 of those little bottles on most domestic flights. Some FAs say they've written to management about it several times but nothing has been done. A few weeks ago on a DFW-SFO flight the FA was so apologetic they ran out of champagne that he gave me and my friend each a bottle of chardonnay to go
.