Nice track, the interesting fact is how is the piece held in place so the milling machine can process it in 3d. I assume the 3d milling machine processes the part and leaves some supporting brackets somewhere which were cut off manually.
Does anyone have access to a 3d milling machine? Can he confirm or explain how is the piece held in place ? I simple planar CNC router with depth control should be able to make the part in a 2 part process, front milling -flip part/block - back milling -then remove needed supporting brackets and grind it a little. If somebody can acces the machine for free, I believe the cost of the material is less than ready made curved tracks. So Rolf, find someone who works with a CNC router and convince him to convince the boss and etc to leave the machine running one night. There's almost no labor involved except for submitting the file to the machine and securing the Alu block to the table. There's got to be some engineers here working in designing and producing parts for the industry/market.
If a cnc planar router with depth control is to be used then the key is to manage to make the front and back milling to coincide after flipping the piece, while a 3d milling machine wouldn't require that and will do all the milling with the piece standing upright.