Cost for the chassis - no bending, only cuting - was U$ 8.12. The smaller front panel, where the headphone jack and pitch bend/mod wheels are mounted, was U$ 4.49 (cutting + bending). The front panel (also cutting + bending) was U$ 19.20.
Those parts were zinc coated at another company. Total cost for the zinc was U$ 26.98 (that includes a few other small parts, such as brackets and keyboard supports), and painting added another U$ 28.78. All metal parts added up to some U$ 90, which is not bad!
I could have those cut in stainless steel; would be a bit more expensive but there would be no need for zinc coating and painting. However, I think stainless surfaces get scratched far more easily and they are hard to repair. Aluminum was another option, however anodizing such large parts is not practical, so all parts were manufactured in 1.2mm thickness carbon steel. The chassis required some aluminum brackets for structural reinforcement; the weight of the boards was causing the chassis to bend too much.