I don't necessarily mean to advertise, but:
I have to admit, it's a good deal. If I hadn't been working there for over three years and wasn't sick of all their food, I'd be going there for this. Almost every table that I serve, AT LEAST one person goes for it. And out of the x amount of people I serve that night, maybe 4 or 5 will ask for boxes to take something home. That's about 5% of the guests. Most eat all three courses, no problem.
Getting three courses for $13, obviously large quantity for a small price is what entices us about this offer. Quantity is a factor that motivates our food intake. It's been observed that as the size of the portions increase, the amount of food increases correspondingly. As we saw with the Bottomless Soup Bowl experiment, and with the macaroni-and-cheese experiment in the book, the portion determined how much was eaten. I notice this every single time I work to know this is a valid observation. For those who order the 3-for-12.99, they end up eating a significant amount more than those who just order themselves an entree. Because they have 3 courses, their portion is obviously a lot larger. So whether or not they are just as full as the person who ordered just the entree or not, they continue to eat because the food is accessible and enjoyable. The more food that's ordered, the more potential you have to eat it, and chances are, you will.
Another reason that contributes to why all 3 courses are usually finished and enjoyed is due to sensory-specific satiety. "Serving only one dish or eating the same food repeatedly is enough to blunt anyone's appetite"; the more of a variation of foods we get to eat, the more we enjoy those foods individually and collectively. If the 3 courses consisted of an appetizer of spaghetti, followed by another serving of spaghetti, and then spaghetti for dessert, it's highly doubtful they'd finish the second serving, or even like it as much as the first, and let alone touch the third. However, because all 3 courses at Friday's vary in taste, we enjoy this experience more and feel as if we ate an overall balanced meal. We tend to get sick of the same flavor if it's all we are tasting over and over, and Friday's makes sure that doesn't happen.
Unfortunately, I am a culprit to serving fatty, unhealthy, over-portioned foods for a living. I engage in watching people eat beyond satiety, and yet continue to serve them course after course. However, I know it's the quantity and variety of foods that we offer that motivates them to continue to eat, so I don't stop them because I figure it's okay to treat yourself once in a while. It's our everyday regulars that I'm worried about.