I think I'm sold on the knee ascender. Might not want to use it all the time, but it's worth having in the bag. They're pretty spendy to buy. The cheapest is the SAKA @ $140. Looks like you could assemble something functional for $100 tops using premade components of US or Euro manufacture. Even cheaper if you went Chinese, or sewed the webbing yourself. Are the purpose built units worth the premium?