The gouged pink foam divots are obviously ravines, can't you tell? :)
If I had to do it over again I would use bark nuggets for the stone "cliffs". Cut pink foam just doesn't sell it. I made a couple hills with the barky texture and they look way better. Oh well, it was my first go at it.
Don't even know about the price of the whole thing, Not too bad but not peanuts.
1"x3" poplar for all the wood "trays" so they are nice and durable on the sides.
1/4th MDF on the bases (would do plywood now for nicer looks).
Pink foam to build up the middle and hills.
Spackle to even it out, particularly where the foam joins the wood sides.
Sand/sawdust mix sprinkled on woodglue for ground texture. (maybe just sawdust next time for less grit)
Painted and drybrushed browns.
White glue and a couple different shades of static grass on top with a home-made static grass sprinkler.
Access to table saw and good fence to saw all the wood trays precisely to size (20" or 10" on the dimensions, maybe just 23" now)