I have. I used cuttings from gums (cleaned with vinegar) on my boyfriends property, stainless steel screws, and some tubing and rope to make an atom to hang off of it. XD
The screws cost about $20 but i didnt use them all.
The tubing for the atom cost me about $40 (including the joiners)
and i bought a massive roll of 250m of sisal rope off of the internet for around $70.
I still have around 200m left of that, so while it cost a bit upfront i still have plenty of supplies for toys in the future.
so overall the stand cost me $20
the atom cost me like $50
and that little ladder cost me $2 for the balls and i used more wood and rope that i already had
The hardest part for me was making it capable of standing on its own, hence the square shape and why its so massive. I initially wanted to make one of those ones that has a vertical tree shaped branch just drilled into a platform, but i couldn't find a way of making it reliably stay up on such a large scale.