Frank, Raymond's Dad on 'Everybody Loves Raymond", sums up exactly what your guests are thinking - whether they admit it or not - when they see a cash bar. When he found out it was a cash bar at his son's wedding, he said:
Frank: "And, by the way, the broad's family is supposed to pay, and it is to be a full bar free of charge, with top-shelf hooch.
Read your Bible."
then later
Hank (Bride's father): I mean, I like to think that I'm a nice fella, and I was always taught to find the good in people, and I would like to with you, Frank.
Frank: Well, I think you are a nice fella, Hank...
... but I gotta tell ya, you're not gonna find much good in people when they drive all the way to Pennsylvania for a big, long wedding and you screw them on the booze.