Kitty gyms are ridiculously expensive, so whenever we have the materials at hand, we make our own. To make this we used two blocks of chipboard, a cardboard tube, and twine.
Most kitchen cabinet makers, and wood supply stores, have an off-cut bin you can go rummage in for cheap blocks of chipboard. We've been very lucky, we even got ours for free from the wood supply place. They leave a great big bin outside for anyone to help themselves. We chose plain chipboard, not the laminated kind - because you want the rough surface to hold onto the carpet. For the carpet, we used off-cuts of carpet from our bedroom (from when we carpeted it), but you can got o Builders Warehouse and purchase small mats for just R15 bucks!
Simply wrap the carpet around the chipboard, and nail it (or staple it if you have a staple gun) to the bottom of the board. Make sure it's tight! Do the bottom one first, and only do the top one at the end.
You can get cardboard tubes from your local signage dude. They purchase vinyl on rolls like this and always have empty rolls to throw away. We bought a roll of raw twine (also Builders Warehouse), to wrap the tube for claw scratching.
To wrap the Tube: Cut a slit into the top of the cardboard tube (and the bottom). Tie a big knot in your twine, hook it into that slit, push it all the way to the bottom of the slit, and then start wrapping. The wrapping takes ages and your hands do get fatigues, but stick with it. The twine is also very rough so wear gloves (I never do and always regret it). Wind the twine around the cardboard, tight as you can, until you get to the bottom. Then hook the twin into the bottom slit and knot it .
We then squeezed in two round pieces of wood at the top and bottom of the tube. To secure this drill in 3 wood screws round the top inch of the ends.
Place the heaviest piece of chipboard (already wrapped with carpet) - upside down, on top of the cardboard tube. Drill a long wood screw into the middle of the tube from the bottom of the chipboard block. This is the stability of the whole gym, so use 2-3 screws to secure it in place.
Then upright it, so the base is standing on the floor. The tube is now sticking into the air, with a wooden disc filling the hole at the top facing you. Place the other section of chipboard on top of the tube, make sure it's evenly balanced, and screw 3 wood screws into the tube from the top of your chipboard panel.
Then simply cover the top chipboard with carpet, nail it in (or staple it), and stand the gym back upright. It's easy to hang toys from the carpet (or nail the string into the chipboard base - and then you'll have a kitty gym which cost you about R30 to make.
We've also made kitty gyms using a thick plank base covered with carpet (the bottom stays open wood), and drilled wood nails into a log off-cut from the yard. The cats love these!