Yeah, anyone who thinks the gold badges in New Leaf are ridiculous should try to complete the catalog in the older games!

999,999,999 bells for the town hall model in Wild World, or the post office model on GameCube, or the ADB in City Folk. Completely insane. This is why I'm not even trying for a full catalog. It would require very frequent play for decades. I'll be lucky if I ever save up 100 million bells in the old games, but a billion? Forget about it.