I know several locals with AP's and for the most part they visit several times a week to eat, drink, golf and occasionally buy merch. They also bring their family members with them when they are in town. I would figure that if a local person or couple visits minimum once a week to eat and have a few drinks, it would definitely add up over the course of a year. Thats 50+ meals and booze per person which is more than the average guest would eat/drink over a 7 day stay. Add in the additional sales the locals bring to the 47 festivals that Epcot has per year and its a pretty good chunk of change.
I am sure there are locals with AP's that dont spend much and mostly go to ride a few rides, but there are also many out of town visitors that do as much as they can to limit spending as well, i.e bringing groceries and eating off property. Just my take on it. I have no idea what the actual numbers are.