When farming royal jelly solo, is it worth it to go for the 4th key?

It wouldn't be hard to estimate the value of the room. We know how many boxes appear.

The big unknown is what your time is worth. The two southern rooms don't require you to kill the monsters. They require only that you hit the buttons. So maybe you can rush through them quickly, saving yourself some time (but losing a little reward).

Sorry, but I don't have a better answer than that. Maybe someone else will give you their opinion. :)

Tbh i dont think its worth doing the 4th key unless you get elite orb drop from the boxes. You can break the boxes using 2 vials from the top left room.
I ignore bottom right room since it doesnt have many monsters.

You can use vials to break the boxes when you are standing on the starting button on the top left room, then you can determine whether or not it is worth it.

As Turbo-Nano and Midnight-Dj point out, it's a great idea to break the boxes ahead of time.

(I didn't think of it, just because, if I'm going to do the Royal Jelly Palace, then I'm going to do all of it.)

What Bopp said.