"Manufacturing" in orbit doesn't reallyv make sense, you'd need to launch not only 100% the weight of the spacecraft (so already you've not saved any money) but also the weight of the equipment to build the spacecraft and possibly even more weight of extra material for any waste in the manufacturing process.

What would make sense is if you have a spacecraft larger than a single launch you can launch in multiple parts and connect them in orbit, or setting up manufacturing on the moon where you have access to lots of raw materials so don't have the launch cost of those.