I think both should have discussed before they left - does either one snore? which gives them the choice to room together or get separate rooms ahead of time, bring earplugs, etc.
I know I do, and have been told I sound like a warthog. Fortunately, many of my friends and family I have occasion to travel with/stay with know this, and they snore too. But I've also been in the situation with new friends, going away, and needed to share a room. I am up front and say hey, I snore, and will also bring earplugs for everyone to use. It's never been an issue, even when the next day they'll tease me about being so loud. But I think they all know that its nothing that can be controlled.
B was out line in asking or expecting A to pay for the pricier room