NICE RACK!!! i always like saying saying that...lol
from what i can tell....it appears that metal brackets were used on every shelf, that can add up quick. also the cost of the flex watt and thermostat could be included in the price?
other wise i cant see materials being that much either.
i will suggest that you rip some strips for center support. i have a diy melamine rack that is wide and its starting to droop and bind on the lower tubs.
when i get a chance i will take a pic of it. doesnt droop enough to see it just enough to bind a few tubs. im planning on taking it apart and re purposing it into 2 smaller racks anyway.
adam jeffery