Fit and finish
These are compromises that are completely valid in the cinematic camera marketplace. If you look at the recently released Blackmagic cameras, they're well made. The Cinema and Production cameras have a solid aluminium (aluminum) body, and the fit and finish is very good. What they don't have is a large number of controls. They certainly don't have "one control per function".
Nor do they have extensive built-in facilities for rigging or carrying and supporting. This is part of the "pact" with users: the cost is very low, but the onus is on the user to rig the system so that it can be used in whatever role it's chosen for.
Note that the fact that there is a crucial difference between these cameras being basic and being badly made. They're not badly made, because that would be a false economy for the manufacturers, who would have to spend a fortune getting them fixed under warranty; and the customers would hate them. It's better to keep them basic but good.
Here's the point around which all of this discussion revolves: it all depends on the cost of manufacturing. Yes, there's economy of scale: the more you build, the less it costs per camera. But some things are intrinsically harder to make. This is why a T-shirt is cheap and why a sequinned evening dress is expensive.
When you look at top-end cameras they're typically festooned with controls, flaps, multiple handles and anchoring points, and all manner of intricate engineering, not to mention OLED viewfinders and expensive control panels.. And all of this stuff is built to an industrial strength: it's no good having all these features if they break off every time you bang the camera against the wall. And the parts, of course, cost more.
There's also the question of how much research and development a company has put into their cameras and - especially - their sensors. Companies like Sony, who make their own sensors, can justifiably charge more for them, especially of there's some aspect of their product that performs better than the competition. For example, whatever you think about the F65 (and I think it's a pretty fantastic camera) it has a sensor which is unlike any other camera out there. It also has a mechanical shutter which - guess what - won't be cheap.
So, high quality, intricate engineering is expensive. It's nothing to do with the picture, but it's everything to do with what you'd want in a camera if you had the budget.
And that's just the mechanical side of things as well. Electronically and digitally - well, it's not quite so clear.
It's tempting to say that your data is going to be safer on a more expensive camera, except that there's really no reason to think so any more. The only way in which more expensive cameras will be safer is if they specify storage media that has a higher reliability rating. They can also offer workflows that are so locked-down that there is little chance of losing data by accident. But, mostly, these are precautions that you can take using cheap cameras as well.
It's also true to say that more expensive cameras will probably have more thoroughly tested software that almost never crashes or gives unexpected results. On-board signal processing may be more sophisticated and capable as well. In a sense, the new crop of "raw" cameras outsource the onboard digital processing to external software. There's nothing wrong with this - it's just a different approach. Remember that it's very expensive to keep full-time specialist developers employed, and the more you test your software, the longer they have to sit there, drawing their salaries, until the product finally ships (and long after, one would hope!).
There is one other way to look at this: let's say you have a tendency to lose or break cameras. Wouldn't you be better off losing or breaking a camera that was a tenth of the price of a more expensive one that you could lose as well (and which was perhaps more likely to be stolen?)?
The whole reason we're having this discussion is that "you get what you pay for" isn't necessarily true any more. You have to look at multiple factors. You can't say one camera is "better" than another one unless you take all the relevant factors into account.
More than ever, you have to really know your subject when you buy a camera today.
But it's a fantastic choice to have! Great pictures are more accesible than they've ever been, and if you want the sort of engineering they build aircraft with, you can have that as well if you're prepared to pay for it.
I wish the person that designed that aircraft lap tray would have a go at making a camera!