To explain how sought after it is, a short anecdote; Some collectors will buy "Alternity Cliffjumper," a $50 toy in japan, specifically to give its head to the $10 2006 classics cliffjumper.
That is because it is a cheaper alternative to getting this set.
This set's main point was to give cliffjumper a more cliffjumper like head.
It also gives you interchangable faces, a new spoiler, and new bumper guards, but everyone wants the head.
If you have this set, everyone hates you.