I think a lot of things actually fall into that category. One thing Disney has gotten a lot better at is that they no longer undersell themselves. If something is worth a lot more than they're charging for it, they seem to be much quicker at determining that that is the case, and at adjusting pricing and/or the offering so that there is a tighter correlation between value and price.
I think the best example of this, though, is admission: They've totally changed the way they price for the fifth, sixth and seventh day of a vacation. The difference is remarkable.
Regarding the party itself, I think it is worth it as a once in a lifetime experience. I wouldn't go back and do it repeatedly.