Depends on what the favor is. Things like candy should be one per person generally, but a bottle of olive oil or wine something like that could be per couple.
My cousin had picture frames as her escort cards/favors. They were nice and it was one per couple, which totally work... except she lumped my three adult siblings together (ages 22, 25, and 29). Um, what? I am sure 3 people living in three different homes can easily share a picture frame.
Be smart about it, don't be cheap, and you should be fine.
Yes, it really does depend. If it's a small gift item then one is sufficient. If it's something like small chocolates that you can put in a gift or favor bag then three or four per guest is sufficient.
Re: Favor Quantity!
My cousin had picture frames as her escort cards/favors. They were nice and it was one per couple, which totally work... except she lumped my three adult siblings together (ages 22, 25, and 29). Um, what? I am sure 3 people living in three different homes can easily share a picture frame.
Be smart about it, don't be cheap, and you should be fine.