What is Ya Thank??
1.
A sarcastic rejoinder feigning gentle surprise at another person's naive, glib, obvious, half-baked or banal observation. (abbrev. of "Do you really think so?") cf.
Person #1: "Gee... outfitting all my bridesmaids in Vera Wang and Manolo Blahniks might eat into my bridal budget..." Person #2: "Ya thank??"