enclosure fabrication resources for the upscale hobbysist
I have seen a friend of mine, a freelance electronic engineer making the enclosures for his designs.
He mostly uses off the shelf aluminium enclosures which he customizes with the following method.

He uses a cnc mill to engrave his company logo and various labels that go with the components on the panel like the "clip" in your image. He then uses black nail polish to fill the engraved words. When the nail polish has dried he uses a flat piece of PE or PTFE (whatever is nearest his hand at the moment) to scrape the excess paint off the surface leaving the engraved words intact.

The result could not be better and looks just like the enclosures in your image.
As for the cost, it doesn't cost him nothing because he own the cnc mill so I don't know if it will be expensive to have someone mill it for you..

Another way of performing the engraving if by etching away part of the aluminium. I have done if by using the toner transfer method to cover everything on the surface except the parts I want engraved. I then submerged the piece of aluminium in ferric chloride which ate away the uncovered metal pretty quickly. I then proceeded to paint and scrape it with black nail polish.

The latter method produced an inferior result especially when there are straight lines involved but it's dirt cheap and you can do it at home.