I suspect the overall opinions may be colored in part by the specifics of the OP.
In the specific situation of the OP I put zero responsibility on the snorer because:
1. There is no indication that non-sleeper ever told the snorer it was a problem, so snorer wasn't given an opportunity to fix it.
2. Non-sleeper did not deal with the snoring in a reasonable and efficient manner - they stewed about it for several days and then booked a more expensive room.
3. They actually had the gall to ask snorer to help cover their expensive room which they booked without first consulting snorer.
So (IMO) in this particular situation snorer owes non-sleeper nothing. And non-sleeper is on the hook for paying for half of the original room as originally agreed.
I imagine the tone of many of the responses would be different if the situation had read:
Person A and Person B go on a trip. On night 1, Person A snores so loud that Person B can't sleep. Person B even tries using ear plugs, but it doesn't help. The next morning, Person A mentions the snoring to Person B and admits that he wasn't able to sleep at all. Person A laughs and says "haha, yeah, I always snore like a freight train - ever since I was a kid! Nothing I can do about it, but I bet you'll get used to it by the end of the trip." Person B inquires at the front desk about another room, but discovers the only one available is an expensive spa suite.
Person B wants to ask if Person A would be willing to split the cost of both rooms and alternate who sleeps in the nice suite for the remainder of the trip. Is that okay?
Because person A knew they snored. Knew it was loud disruptive and they couldn't do anything about it. And person A addressed it like a mature adult.
And of course there are a ton of different scenarios in between. Fundamentally, I think both parties have a responsibility to be mature, understanding and as accommodating as possible. Unfortunately in the situation in the OP the non-sleeper never gave the snorer an opportunity to do that prior to asking for money to stay in an upgraded suite. In the situation I presented, the snorer was unquestionably rude to not mention the snoring before agreeing to share the room.