An Annual Pass is $798 (including tax). You said that you would pay $408 for a 4 day pass. So if you are planning to go in October for at least 4 days, you would spend $816 on tickets for both trips. That makes it a small savings of $18.
Besides the small savings above, remember that there are sometimes room discounts for AP, there are always table service discounts, and some merchandise discounts as well. Plus, if you're NOT staying onsite, the AP gets you free parking (staying onsite does also), but with just a ticket, you will pay $20 per day parking.
If you're going in October for the
MNSSHP, there are usually select dates that you get a small discount on the tickets.
Also, the Annual Pass includes Photopass.....meaning that you can download for no additional charge all of the photos taken by a Photopass photographer and all ride photos (you can decorate them and download them for up to one year from when they were taken). With just a ticket, you would pay $149 for the same photo option.
Now, the negative side of an AP.....you find yourself going for another short trip or two or three, because you have the AP, lol. But, for instance, the
MVMCP is discounted and think of all those other holiday fun times!