$5000?
I will concede that this is the same angle in which the factory Boxster hard top looks less desirable.
I agree with the hard top vs. conversion comment. It really does seem like a minor feat to install that thing.
Check out the install instructions.
http://www.zeintec-usa.com/FAQ.htm#Q7
Remove the clam shell's 6 bolts, remove the trunk lid's 4 bolts, add 100 pound top, wire up the new brake light. The web site estimates it as a 2 hour job.