If the 16" Fuchs set is nicely polished and date matched together with zero flaws probably $1000-1500 a set to the right buyer. $800 if you wanted to dump them quick. Probably you could hold for 1200 and get it. Again assuming very nice wheels.
Check out
www.wheelenhancement.com to get an idea.
The last set of 4 I had was 15x6 real Fuch wheels with caps in medium shape and I sold them on the cheap for $500. 23mm offset which did not meet my needs.
In my opinion Boxster 16x6 should be about 50 each and maybe 75 for 7s. The Porsche owners treat them as pure take offs. I have passed on similar sets for 300 with new tires! (read: factory take offs from the jump)
Just be careful Super VW.