Those machines required a large number of precision stampings and small machined parts. Lots of custom tools and dies. Tooling up to make all those was a big job. Once they had all the tooling and plant, the Model 15 was cheap to make, despite its complexity. Teletype tried making a cheaper, simpler Model 26, but it cost more to make than the Model 15 because the manufacturing process for the heavy-duty machine was working so well.

From the beginning, most Teletypes were rented, not sold, and came with maintenance included. So the machines had to be reliable. The Model 15 seems way overdesigned. Flat parts were both hardened and Parkerized, a caustic process that deposits a rust-resistant oxide and turns metal grey. (Sometimes used for guns.) Fine-thread screws. Lock washers on every screw. Insulation that won't age or crack. Plus, the keyboard, typing unit, and motor are all very easily replaceable; they even disconnect electrically and slide out. The screws and round parts are all custom. They must have had a huge number of automatic screw machines turning them out. All round parts fit precisely.

This was not made in a small workshop. More like a factory that covered a city block in Chicago.