Production Timeline for Mature Metal Devices

I’ve been curious about the extended production timeline for their devices. I don’t know much regarding machining or what goes into working with stainless steel. Do they have a lot of waiting time between steps? Is the maker so busy that only limited units come out at once? Obviously every piece is distinct, and I get why he avoids holding unsold stock in various sizes just hoping for buyers. Just wondering how many hours go into crafting each one.