First, I'm not surprised that a few people have pulled out of those plans. Stop and figure up the range of what people will be spending for your wedding, total.
Whatever numbers you come up with, I'm sure it's a lot. And the ongoing things that come up in other people's lives are and should be their main priority--- not your wedding.
Any of the numbers you've figured up- how many of those people would YOU hand over that much of your hard earned cash to? Again, regardless of the rest, you ARE asking a lot. Many guests might be on the edge of if they could swing it or not and as it gets closer to the time to pay up, they have somewhat different circumstances and have realized it's now farther out of their comfort zone than they want to go, after all.
As has been mentioned, you probably don't know their full situations anyway. Maybe someone is pregnant or their spouse has been diagnosed with cancer or their job is on the line- there are many expenses or threats of future expenses that can come up unexpectedly, that they aren't necessarily ready to disclose. There's also a time cost, aside from the financial cost.
As far as who's similarly expensive things you've paid for, well times change, Don't they? You're likely all in a transitional stage of life, where your friends are going from being young and free to settling down and getting more serious about life. Buying homes, getting married, having kids--- or planning to. There's a stage of life where it's still fun to blow money to hang out with your pals and then it passes into a stage where all that recedes into the background because people have more grown-up concerns.
So, they have told their change in plans to the person you put in charge of handling it. The idea that they need to consult with you first is incorrect, in my opinion. That also smacks of you thinking it's a discussion, when their change of plans does not need to be approved by you and is likely not something they enjoy doing.
Anyway, with ALL of it, please realize your wedding is really, mainly, a series of expensive, non-necessary luxuries that centers around you. It's not that important to others. Treat it accordingly.
Expect more of this kind of thing and graciously accept it. Anything else puts you firmly into bridezilla territory. If you don't want to mark yourself as a self-centered, immature, spoiled brat, keep these feelings to yourself (and on forums where you're anonymous). That's my advice.
Now, get on the internet yourself and find a suitable place for the remaining guests to stay. Just get to it and see what you can do. It might involve downgrading the luxury or kicking in some more money of your own. If you can't swing it even after being more flexible, then cancel it and expand the plans for your other hen do instead or whatever. I think you'll feel better after you get this settled. Best wishes.