YABVU.
I've only ever been to one wedding where it was a free bar, and it was in a hired barn in the middle of nowhere, with no corkage costs. So it didn't cost the bride and groom THAT much to get everyone pissed for free, especially as there were only about 50 guests and they could just stock up with a few crates of cheap plonk from a cash and carry.
At every other wedding I've been to, as others have said, it's been a pay bar with perhaps a drink for the toast, or wine on tables, as well. I never expect anything other than that and certainly wouldn't expect people to state on the invitations if it was a pay bar.
But what I really take exception to is your feelings that this couple are "having a wedding they can't afford."
What, should you not get married if you can't afford to get all of your guests pissed?
Should you save up for another year or two, or spend money that could be better put into something such as a house or family car, just to placate the snobbish, guestzilla element who resent paying for their own wine?
This REALLY pissed me off.
I should add that, when I got married, I was absolutely broke, but wanted a big and informal wedding with all my friends. No flowers, no photographer, no wedding cars, no bridesmaids, no ushers, none of that. Just a relaxed party for all to enjoy.
We paid for our guests to eat twice - a big lunch and an evening buffet - but there was no free booze at all as we simply couldn't afford it. All the guests knew this beforehand and had the option either to bring their own bottles of wine, or use a cash bar. Nobody minded one bit.
But perhaps in your world, the likes of us shouldn't have got married at all. Or should perhaps have only invited immediate family so we could afford to buy them wine all day.
Maybe you shouldn't go to this wedding. If I'd had a guest who was looking down on me for being poorer than them and not doing things "properly" it would have made me very uncomfortable and really quite saddened.