Those expensive keyboards are custom keyboards. They are made in smaller number than mass-produced Filcos, CM QFRs, Blackwidows, etc. So the price is higher at least because of that. That includes custom case design and execution, custom plate, custom PCB and controllers, firmware, etc. Secondly, the materials used for those custom cases are usually better and more expensive. For example it can be machined aluminum--a hefty amount of it--which is then polished/bead blasted and anodized (extra to the price). There are even possible other composite parts like machined and polished brass plates, etc. Price for all that is quite high because of materials, cutting, finishing, and the relatively small number production. If 1000 were made, price per unit would have been a bit lower. But they are made in much smaller numbers, like 10-100 of each kind per production run and that's it. Acrylic cases are also custom designed and made so they are cheaper than aluminum but more expensive than standard cases.
Better than standard keyboards like Filco? Not really. Define "better"? They are just different. They are fully custom, made from more solid/heavy materials so they absorb vibrations really well (they sound very different vs. a regular keyboard), and they are usually fully programmable. Plus most allow for custom LED layouts and modes. Filco and Ducky keyboards are still excellent, for example, you're just paying for mass-produced keyboards made out of cheaper materials. But their PCB and build quality is still excellent. If you want eye candy and better denser materials and don't mind paying more--get a custom keyboard. Otherwise, you'll be happy with your Filco--it's a great keyboard.
