There is a lot of factors on when it breaks even because it's more than just tickets.
The discounts from it are basically the same as a disney visa card so if you already get those discounts, your not going to save any money on your trip from that. If you don't then it's roughly 10% off merch and table service (some exceptions to that) and if you like to spend money when on property that adds up fast. You also have to remember to keep asking if they have a discount as very few cast members ask you and then know the tricks like if your going to buy a soda, get it in a gift shop that takes your discount and not the kiosk or outdoor vendor.
Room discounts aren't a huge savings if you even get a better deal. I booked an AP discounted room trip about a year ago at a room I didn't want that was more money.. luckily a couple weeks later I noticed the lower cost rooms opened up and switched.. when I finally got close to leaving a non-ap discount that was better came out but it fell into the complicated to understand change fees so I actually ended up spending more for the room than someone else just taking a normal discount. (only about $30 more in total, but still more). Basically don't expect to save money on your rooms with the AP discount, it's very minimal from other discounts and cash back or point from a good credit card will be more valuable than an ap discount.
Now where it can make a huge difference is parking. If your a use a car disney visitor and your staying off site, parking adds up really fast and a nice savings..
Also if you like getting memory maker, you wouldn't need it and you'll get all your photos and they don't expire as fast so in my eye, it's a better deal so there is a big savings cost there..
If you like tours, parties and some limited run events, many of them have some sort of AP discount.
Now one that can be huge is you qualify to buy a tables in wonderland card that gives you 20% off most table service and some counter service. It's also the only discount that includes alcohol so if your a big table service group and like some drinks with it, it makes a huge difference (but be careful where it works as it might be hard to break the card even if your just a couple visiting)...
And last, not everyone needs an annual pass in your group to get most of this. It's not uncommon to get 1 annual pass for the extras and then it's easier to break it even or save money..
now for the catch 22:
A down side of having an AP is your going to want to come down much more often. When you have a ticket in your pocket, air fare is cheap and you see a room for not that much money you will have a hard time not taking a weekend or long weekend trip. You'll start to read and hear news about something interesting happening, opening or closing and it's a lot easier to afford coming down when you already have a park ticket..