Make blueprints both fun and let PK-trolls have their fun as well:
Gunrunners sell random blueprints for cash, but as a quest.
Every hour (or whatever) a new blueprint is randomly selected. You go talk "Hey, do you have some blueprints?" and in reply "Yeah. I have an Advanced Power Crowbar blueprint for 5000 caps, but you'll need to do me a favour if you want to buy it. Interested?"
The quest would create a public instance on the world map (yellow dot) somewhere near-ish to boneyard in town squares near the sea. You go in, kill random enemies depending on the blueprint, pick up a briefcase and return it to gunrunners. The briefcase would require 299 lockpick and contain beer so opening it would be pointless.
After you return the briefcase: "Ah! Good beer is hard to get these days. Thanks." reply "So what about that Advanced Power Crowbar?" and you can pay caps to get it. If you lose the briefcase, you have no penalty. The next hour (or whatever) when a new blueprint is selected, you can take the quest again, but you will need to pay 500 caps before. "Hey, you're that guy who lost my beer! If you want to do business you will have to pay me back for it and bring me a new case."