What’s up with watermelons and eggplants?

Why is it you have to go through so many steps to get 1 watermelon or eggplant? I cleared 3 plots, got a bunch of tiny plants, but when the merging was done, ended up with 1 measly watermelon. I fare only slightly better with eggplants.

Is it that they are high value that the return is so low?