It really depends on your crowds background. For example, I’m military background and fiancé’s family is heavy drinkers(sounds worse than it is, they can throw down though 🤣), so we’re planning on some heavy drinking, probably averaging 10 beverages a person. I know we’ll have a few that won’t drink, but others will have 15-20. If your family and friends are classier than ours, probably 3-5 a person is a safe bet.
There is no one size fits all because every group is different. Some are heavy drinkers, some don’t drink, while others don’t care either way. Some drink only beer and wine while others won’t touch those and drink liquor only with mixers.
You have to ask your guests who will be attending what they drink. Don’t offer anything you can’t afford to serve because guests are not responsible for covering the bill.