Oh it so much depends on what you are bringing for food. Take along capellini or orzo for your carbs and you can put 25 lbs (40,000 kcals) in one BV500. Flavor with carmelized onions and tomato paste you've cooked, dehydrated, and vacuum sealed yourself. Add sliced pre-cooked meatballs you dehydrate. A gazillion other combos. A dehydrator costs $60-$130 - the same as one or two cannisters.
I just packed 6 BV500s for 6 people for 12 days and the food is really good.
If you go the Mountain House freeze-dried route, expect to get only half the carbs in a cannister. It may be light, but non-oily food is at most 4.5 kcal/gram, more like 3.5 to 4. Freeze dried food is full of air, and that means more 2 lb cannisters, more total pack volume, larger packs, and suddenly freeze dried doesn't deliver light weight anymore.
Things like coffee and cocoa have little to no nutritional value and take up a lot of room. OTOH, flavor packets (tea, Via, crystal lite) can accomplish the taste variety without much space. Some cereals are dense, others mostly air, though all have roughly the same carbs/oz. Nuts, chocolate, and dried fruit pack densely.
One idea is to dump orzo or somesuch around your other stuff to fill the gaps. It's quite enlightening to see just how much "wasted" space there is in your cannister.
Before you buy/rent the cannisters, measure some boxes, do the math, and see how much you can fit in a given volume.
Like so many things backpacking, lots of planning makes for a much improved trail experience.