Um push a broom, stock shelves, tweak procedures, train, build other things. Its not like you snap fingers and can just start building bikes right this moment. There is a small motorcycle manufacture that I have visited several times here in Michigan and its not as easy as it sounds. You have supplier quality issues to discuss and they are probably trying to get as many jigs and high process time issues out of the way so when there is need they can build as many finished product as possible. I would think that building up engine assemblies and frames takes a lot of time. Bolting these things together (as we should all have some perspective on) isn't as long of a process. Also consider building and buying in bulk saves on cost both before and after a machine is built.
In the world of economies to scale I can appreciate what GG is going through right now.... glimpse into something I had a front row seat with. https://youtu.be/acVuYHuO8GY
--Biff