I think one neat idea that no one has suggested yet would be to make it so that your bed couldn't be placed too far underground.
Since I'm assuming most of the really nasty encounters happen the farther down you go and the really good stuff is really far underground, bed-spamming wouldn't be such a huge issue since you couldn't use it when you really wanted to. Therefor you can make the bed cheep and newb friendly while still not game breaking. I'd say you couldn't place a bed any farther than you could encounter gold... then again I've never seen any gold so idk how far down that really is... or possibly not where you could see lava... something like that.
Other than that I like the idea of the expensive bed you start the game with, though that would make it hard to use it for decor, and I like the cheap bed with debuffs. I also really like the idea of making the beds more useful the more expensive they are.
I hope my idea isn't too horrible. :happy.gif: