That's all engineering. You can put no money into engineering and put out a heavy piece of junk that just works, or you get something that is highly engineered that will weigh the least in its class. Once something is engineered (which in itself costs a lot of money), it will cost more money to produce, because of the tolerances you may end up with a lot more dead/wasted pieces, etc.

It's also a pretty bad example. If you want to compare a $200 wheel to a $1000 wheel you are comparing a cheap low end wheelset to a high end racing wheel or a low end carbon wheel. That engineered wheelset is also going to be a hell of a lot stiffer and have more reliable hubs, lighter spokes, etc.

Then when you get into specialty materials like titanium and carbon, there are different grades of the material. A cheap carbon frame would not be as good as an expensive aluminum frame, for example.