Extra adult fees:
$25 for deluxe, also at Swan & Dolphin
$15 for moderate
$10 for value
Less at Fort Wilderness, but I'm not sure what -- maybe $3 or $5
Even if we felt okay about not registering our extra "adult" (our oldest child), we wouldn't b/c we do e-night and need him to have a resort i.d. Lately, Disney asks the kids' birthdays when you book rooms. They used to only ask ages, and I'll admit that last year I did not say he's 17 but will turn 18 before we arrive -- I just said he's 17.
We're moving to two rooms at the All Stars this year b/c the extra $25 a night for my oldest son added $200 to the bill at a deluxe.