You're thinking along the lines of what you pay for parts at the counter. If you have never taken your car to a shop to have it repaired, you've never realized how badly they mark the parts up. That, "$10" worth of bearings and races in reality, at their cost, is about $30-40 worth of bearings, races, and new grease seals. You will subsequently pay easily double that for the same set of bearings, and you'll pay for a few hours of shop labor while they disassemble, clean, replace races, repack, and reinstall your wheel bearings/hubs.
For a hub assembly the part will be $75+, and list in the $150 range, but you will pay for that, and for the tech to bolt the new hub assembly on and that's it.
I don't have labor manuals at my disposal, but I would think that you'd end up leaving there with a much lower bill for the replacement of a hub assembly than a set of adjustable wheel bearings. So, for the majority of customers that don't work on their own vehicles, this represents a potential savings. For the techs--it is much easier for them, too.
For those of us that work on our own cars/trucks, they suck, because we have to pay much more for that hub assembly over the counter than the average joe.
However, I believe that the end cost is probably less for your average joe that has car with hub assemblies, takes it to a shop, and goes to the shop where all the customers must grab their ankles before entering, and pays big $$$ for the job.
Now, the bearings that must be pressed from the knuckle, I'd bet they really get an arm and a leg for them. I know we charge $45 to have that service done, and that is after the shop has charged you to disassemble it and reassemble it (they send the whole knuckle in). So, double that $45, and add whatever you think they get for completely removing a knuckle from the vehicle, and that will become an even bigger repair bill than either of the last two examples.
For the DIY guy no question the tapered bearings and seals are much cheaper (and a better setup IMO anyway).
When I worked at Autozone, greasable joints were $7.99 and non greasables $12.99. That's a pretty big jump.