Get 2 2x4s that are approximately the height of your ceiling. Then buy a 1x6x8. Cut said 2x4s to roughly 1.5" less than the height from floor to ceiling. Screw these together to create a 4x4 (or just buy a 4x4 if you're lazy and don't want the extra work, or they end up being cheaper). Cut a ground plate out of the 1x6 for the bottom and attach it to now 4x4 stock. This probably only needs to be around 8" long, but you'll also need one for the ceiling. You've now got 6.5' of 1x6 left. Cut that into roughly 3 equal pieces (about 2' long each) and notch them so they fit around the 4x4 post (you can use those grey shelf brackets or leftover bits of 4x4 to provide extra support).

Attach the extra 8" piece to the ceiling in the corner you want the post to be in. Don't attach it to the upright like you did the bottom one.

Cover the whole assembly in non-snag carpet remnants obtained from your local carpet place. Using industrial staples works best to hold the carpet in place.

Now, stand the thing up. The ceiling mounted board will help prevent you from scraping the ceiling up as there should be a slight interference fit. Then toenail or drive screws at an angle into the upper board to secure it.

Viola - you've just created a space saving scratching post for under $30.

this is coming from the guy that cut his counter tops wrong? :P

Well, there is that. But more of that stemmed from using the wrong tool for the job. Mostly because the right tool was damned expensive and I thought I could make it work.

Lesson learned there.

But mind you, this is definitely easier...

If y'all want to build it, I have the saws and space and tools to make it happen.

of course, it will lack the cachet of the store-bought version....

Nope - it has the chance to be significantly cooler as the carpet remnants can be chosen for maximum effect rather than the boring beige that always seems to show up on them now.