My experience with my cats, but keep in mind it's totally based on preferences of the particular cat, has been that when a cat prefers carpet, they will not use sisal at all. We have a large armarkat cat tree, which I got for about $90 dollars a few years back. Only Lacey uses the sisal part when she climbs it, but not to scratch. The carpet part is very worn, but the sisal looks new.
Being that post you linked to is about $70, I would look for a cat tree made of carpet on Amazon. Most time they have free shipping so you end up paying about $100 flat.