How much memory do planes take?

I have a system that loads in a plane scaled 25x so basically ends up being 250x250 in its bounds size.

This system shows the plane the player is on and the 8 surrounding planes to that one. as the player moves these planes are generated and destroyed as needed.

On those planes I only generate the land decorations that are within view distance of the player camera so while the planes are a little large, they are not fully decorated with the trees and grass for the full x and z dimensions.

Is this the best way of going about it? Are my planes too large?