It's a combination of ALL attacks requiring consumable items, battles only giving you coins, not experience, and thing stickers causing some really stupid trial and error stuff. In particular, the intended way to figure out the bosses' weaknesses appears to be to lose against them once so you can see their attacks so that you can hopefully figure out which thing stickers (which you may not have even found yet) you can use to counter them. That's not to even mention the environmental puzzles involving thing stickers. Also, there's of course the fact that trying to use a thing sticker, even in a wrong situation, uses it up, and reaquireing them can be a real pain.