As an AFOL who got into wargaming as an excuse to play with Legos, I couldn't agree more with the ridiculous pricing. This is the main reason I do not do terrain in legos. For example, if I was going to do a 40"x40" SoBH table it'd take 16 32x32 stud plates at $7 a piece...and that just gets you a flat play surface - add in trees and enough plates to make a hill...not to mention enough bricks to make even small fortifications
I play with Legi minis on 'traditional' terrain. It's a nice compromise. Aside from cost, I like to be able to model my terrain myself.
Example: here's a shot of my desert terrain.