Hmmm that's a toss up. I don't think that's too much for 48 invites, fully custom. However, I also really like the idea of only one side customized and then getting something else, like someone mentioned beer koozies. I think in either option, they are unique, fitting with the theme and something that will be useful after the fact.
Re: Beer Coaster invitations
I would make them myself. This coming from someone who is not crafty at all.
I think this is a really cool idea that you're doing!
I am actually having his favorite beer from Maui shipped:)
Here is another 18.95 for 50
https://www.americanstationery.com/shopping/prod_detail/main.asp-pid-2381