I just helped a guy build one for coco. Auto top off and dosing for a 100gal tank. 8 dosing pumps individually dosing all nutrients and ph control. Of course the usual autofeed and drain also. I think you would be shocked at how cheap it can be done comparedto these companies. He can refill, add nutrients and feed plants or adjust feed times and frequency anywhere from his phone.
I'm way to much of a DIY'er to buy one. Seeing how I work in a field that I have to build and repair alot of one off stuff including an auto batching system. The plant is extremely automated start to finish run off of a PLC system. I'm very familiar with this type of stuff.
Not gonna lie though it would be a lot more convenient to just buy a proven system and not have to work put any bugs or brain farts.