No it's not generally 'etiquette' to state it's a free bar on the invite.
We always take cash/cards if attending a wedding (or take a couple of bottles of something if it was a 'bring a bottle' for the evening - been to one of these, was brill, not remotely bothered about being asked to bring drinks, the barbecue laid on = BEST wedding meal ever).
70% of weddings I've been to - free bar mostly on the basis in next paragraph, except a couple of Hindu weddings where there was no bar but each table was given 4 bottles of spirits, mixers, 6 bottles of wine and an array of soft drinks and as bottles were emptied they were replaced!!! Food was soooo fab too.
We provided a free bar in the evening (wine, beer, lager, soft drinks then if people wanted spirits they needed to pay). We took the view that weddings can be costly for people to attend (travel, possibly overnight accommodation, wedding gift etc) plus the bar prices at our venue were considerably more expensive than standard pub prices so we did not think it was fair to expect our guests to have a crippling bar bill because of our chosen wedding venue.
You sound royally pissed off about not initially being invited (rightly so, as best man's partner - ridiculous), which has made you 'pick at' various aspects of the event. If initially you were left off the invite list, either one/both of them utterly loathes you or, it's not unreasonable to think they have not 'cut their coat according to their cloth' and cost cutting measures included complete disregard for their best man and his partner. In which case they've taken the curious notion of 'our day' to the extreme.
I think if me and dh were in your shoes, once we knew I was not invited, dh would have resigned the post of best man and steered well clear of what sounds like a crap day from a guest's point of view.