There are a lot of DIY copies on the internet. If you are a little handy I have seen parts lists and instructions for building a similar solution for less than half the price. Just google “undercurrent” with “diy” or “rwdc” and you will find lots of different forum posts, etc.
I am just waiting for some uniseals to show up in the mail and I am going to be building my own 2 plant system. In any case I really like the Undercurrent 4xl system - a lot. I just can’t spend $1k+ on it when lots of people grow great plants with far less investment.
Here is a link to a system one of the people here built: