Gammerz The blueprint thing is a bit messed up tbh. In the beginning, effectively the only place you could get blueprints was from the people you hired to work in your base (not entirely, but that was the gist). You even had a vendor in your base to sell you base bit blueprints, who just kind of showed up uninvited.
Then they brought the Nexus in, and suddenly you had a machine where you could buy blueprints by paying with stuff you dig up. But they kind of never removed the quest lines from the base specialists that got you those blueprints from before. So the Scientist dude will be like ‘Aha, do this thing for me and I will give you the blueprint for an oxygen condenser!’ and you’re like ‘bought one of those about three weeks ago mate’.
Plus there are things (e.g. glass) which you can still get a blueprint for but you don’t actually need at all, you can just make it, and there are two recipes that make it anyway!
It’s all rather inconsistent and odd, because they never went back and tidied stuff up. I suspect mainly because if they did you’d have pretty much zero reason to talk to the specialists you recruit…