The tray never runs empty as long as there is water in the tank. The float valve continuously feeds water into the tray; the pot sits in a low pool of water at all times. Apart from the valve it is a simple wick system (the substrate itself is the wick).
The Octopot and the Hooch bucket are very similar. The Hooch bucket is the most simple and effective design I've seen so far. When you have the actual buckets, which need to be 3D printed, all you need is some PVC gutters and a $5 float valve for each gutter. Practically Octopots on rails, I absolutely love it. It's demonstrated on YouTube by the maker. Would scale to really large setups at low cost with almost no moving parts (one valve per rail).
The AutoPot valve is patented, so it is a cash cow, but honestly I do not see anything special about it, except for it being really well tuned and of high quality. It's also fair that you can buy all parts separately, even the little silicone cap on the valve which is probably the only part that could wear out or be damaged.