The Goat Bills are such great forgeries that they can fool almost anybody. But Lupin and Jigen just throw them away? And why was Lupin so excited when he learned that Fujiko had the plates, allowing her to make more? He doesn't want them, he tossed out a car-full of the things.
Fridge Brilliance: For Lupin, there's no fun stealing fakes. He is better than that. As for MAKING fakes...
Another possibility is that, Lupin might've figured the plates themselves might have value... or he might've wanted to keep them stashed away specifically to prevent the Goat/Gothic Bills from ever returning to print. Or he was just trying to flirt with Fujiko and only pretended to care about the plates. Really if he wanted them, he had a chance when he and Zenigata were down there in the printing press.
Something similar to this actually comes up in a Red Jacket episode where NASA invents a dirt-cheap method of synthesizing diamonds; When Fujiko starts cooing over a diamond the size of a grapefruit, Lupin coyly asks if she'd like it as much if its resale value was, say, five bucks.
Why does Fujiko feel the need to pull off her pink dress to reveal a camouflage outfit while on live TV? (Apart from Rule of Funny, of course.)
They were broadcasting in the middle of an ongoing gun battle. She even draws a pistol from her cleavage and caps one of Cagliostro's goons with it, when he tries to take them off the air. After a brief cutaway scene, she cracks another goon with a wrench. The dress would've been in the way, so she ditched it.