Definately one of the best lenses I´ve ever had, loved it and still miss it :-)
This is a highend, quite rare lens.. you should be able to get a fair price at a reputable dealer.
If you´re in europe (or have no troubles with dealing with us:-)) you could try:
Arsenal-photo.com
leicashop.com
photografica.com
schouten-select.com
you can get their opinion....
BR
Martin