Sure catmandu. We're actually pretty proud of how inexpensive it is to build these things yourself.
We had some scrap wood in the basement, so that was some savings. The bottom pieces is actually an old door. Then the shelves are the old shelves we took out of our closets. Then we just got some 2x4's and alot of mdf and carpets. Just cheap remnants and stuff. The tube is covered in a big area rug I found on clearance. The tube itself is a big carboard tube from HomeDepot. YOu can also use plumbing pipes and cover them.

We spent about $150 when it was all said and done. Easily you could order one for 10 times that amount.

We went online and looked at lots to see the elements we liked. Then we sort of sketched it on paper. But it was really all just "from the hip" building. Chris is very handy so that was good.

There is a ton of glue and over 5000 staples in it And we haven't even done the sisal rope yet!!

I went on google.com and entered cat funiture to research. There are some cool ones on www.angelicalcat.com and they are over $1000!!