Well, to be honest, I think your numbers are too broad. I don't spend nearly $50 per adult on an average day since we don't eat TS most days. For kids, a range in smaller increments might have been better suited to this. I figure $15/meal for lunch and dinner -both QS/CS per adult. Sometimes over, sometimes under. My DD-8 won't hit $20 even with snacks and drinks.
If I figured days where we eat TS, I figure an average of $35/adult for the TS and $15/QS, so we'd be right at the $50 mark. We can't manage 3 remotely large meals per day, so on days where we eat a QS or TS breakfast, we'd have snacks for lunch and eat an earlier QS or TS dinner.
We don't skimp on food, we're not necessarily light eaters in my opinion either, we just eat when we are hungry and only as much (snack or 3 course meal) as we want at the time. For my family, being full makes us unwilling to go on rides or walk very far
In the end, reviewing our slips (every bit of food charged to the room), we come in at just under $100/day for my family of 4-- 2 adults, 1 - 14 YO and an 8 YO. This is an average of 10 days with one TS/buffet 7 of the 10.