The discounts vary by resort..........interestingly I got 30% on the Yacht Club and 30% on POP............that doesn't sound right..........but that's what my calculator says

. The values usually don't pull that good a discount.......but whatever. The other thing to keep in mind is you're not guaranteed a discount for the room you have/want. I got lucky........both rooms where "standard" rooms and the discounts came up..........but that won't always happen.
One thing, getting the AP for room discounts exclusively, in my mind, isn't the reason to get the AP. We live in NJ and had our AP's since Nov 2016. By the time our AP's run out we'll have visited WDW for 24 days...............that was the driving force for us. We also have the TIW card for the 20% restaurant discount. We love the store discount..........at WDW. The room discount is cool...........but for us.........its the entire package. If you're only visiting for 1 trip, less than 10 days............I don't believe the AP room discount makes it worth it.

My opinion
Doug