This is a simple but effective DWC system that you could easily DIY for much less. The fifth bucket is a reservoir, but this is not a recirculating system (RDWC)... but it works.
IMPORTANT: instructions consist of a single sheet of paper, just an exploded diagram, but it's simple to construct.
Good news: Setup is fast because you get pre-drilled buckets and all of the valves, fittings, grommets, and air stones you need. The kit includes an air pump, too.
Bad news: the air stones and air pump are low quality. You WILL need to upgrade both -- call the Hydrobuilder guys, they'll help you get what you need.
I also strongly advise buying a 1/10 hp chiller, because you want to maintain 75 F air temps and 68-70 water temps. Also, buy Hydroguard for beneficial bacteria (or go sterile via Dutch Master Zone).