..the cost of treatments and sugar are the least of it...the real cost is labor.
I don't think feasibility has much to do with being migratory or stationary...I know treatment free beekeepers that do both....and I know of both kinds of operations that can't possibly run without treatments....not because of the bees they use, but because of overhead. If you have employees (especially if they are treated as you would want to be treated), vehicles, facilities, etc....you've _got_ to bring in the money consistently....any risks or short term setbacks affect everything and everyone involved.
When your overhead is low (no or few employees, modest vehicle and facility expenses), you can afford to rebuild from a moderate disaster. In the scheme of things, keeping bees has almost no overhead when compared to virtually any other business or agricultural persut. Our friend Andrew Munkres grew one nuc to 70 colonies in three years (there were a small handfull of cutouts as well, but only 3 or so). He got the nuc in exchange for labor. He is a skilled woodworker and I'm sure built all of his equipment from scrap and cheap lumber. I don't remember what he did for foundation, but this was likely his largest expense (I know he does some foundationless). He does do some winter feeding to make such increases, but remember he now has 70 colonies for almost free....without having to own or lease a farm.
Working alone (without labor) has limitations. With a spouse or close partner you can probably run 2000 colonies or so if you are using minimal management...you won't have time to retail honey with this many colonies, so it's important to find a way to sell your honey at a premium.
The bulk of the industry makes their money buying and selling the lowest quality product at commodity prices. Their interests are poorly served when the market becomes stratified....when consumers are willing to pay a premium for a higher quality product (think of a class with grades...those getting a D will vote to have the grading be pass/fail rather than letter grades...they will be in the same catagory as those getting an A....OTOH, those getting an A want to be set apart and recognized as superior).
So, in a poor year, no seasonal help is hired, overhead is small, and the small crop that goes for a premium can pay the bills and support you....you simply can't do this if you have a crew that gets a paycheck or the expense of running a large facility. In a good year, a bit of help is hired to handle the load, and an extra large crop allows for upgrades...and nothing says you can't simply store the surplus in barrels.