Extruded aluminium cases are fairly popular for smaller production runs because they're generally off-the-shelf with only the faceplates being custom (usually l

Extruded aluminium cases are fairly popular for smaller production runs because they're generally off-the-shelf with only the faceplates being custom (usually laser cut and engraved). So the fixed costs are basically zero but the unit costs are somewhat high (aluminium is expensive). Lots of stuff is just made in large enough runs that molded parts become cheaper overall (very nonzero fixed costs but very low unit costs).