I may have mentioned this organized event before, run by the biking organization Velo Quebec, here in Montreal.
Its called Le Grand Tour, is generally 7 days cycling, sag vehicles, meals provided, tech support. Usually about 1200-1800 people do it each year, vast majority go with the "sleep in your own tent" option, they carry your stuff to each days destination. This year the cost for this option is $835, so roughly 120 Can. per day.
You figure camping will cost X per day anyway, food Y per day, so the extra is for all the infrastructure setup and all the details others mentioned.
Ive done this with my wife a few times simply because my wife doesnt want to do loaded touring, so this means we can do a biking thing together. Le Grand Tour is also a huge social event, the average age is over 45, so in general its middle aged folks (many single) who enjoy meeting other people and biking. Its perfect for those who have no interest or experience planning a trip on their own, so having a route set up clearly for you, on-road bikers to help with any problems (incl fixing a flat), sag vehicles available if you cant make the days distance, not having to think of where you will stay, not having to think about food....plus meeting lots of people, its a model for organized trips that is very successful.
I believe this year is the 20th year, and I have to say, its pretty well organized.

I think it was pretty smart of Velo Quebec (the bike organization I mentioned that runs it) to set it up this way, it attracts people exactly like my wife (so gets people out biking, which is always good in my opinion), keeps the costs down, and each year they change the destination (nearly always in Quebec, or at least within a 3, 4, 5 hour car distance) so this is great for repeat "customers" as the area changes each year.

They offer limited hotel room options, and have even started another option where for a fee, they set up a tent for you each day (again, trying to attract folks who dont want to even take 5 mins to put up and take down a tent each day) It must be successful, as they are still offering it this year.

Like others have said, organized trips can be all costs, but its great to see that this approach of keeping the costs down can be done successfully. Obviously smaller companies have a different feel with less people, this one really is quite an event just in terms of numbers. Field full of tents etc.