especially rookie cards.....even lower grades like PSA 4 ($1000) ...keep their values.....a PSA 8 is about $6000 US if you can find them
I have a very nice 1967 #92 in PSA 8 that I may post in the buy/sell section one of these days....
I also have duplicates of his 1969 OPC cards including this one on ebay now....(shill, shill)
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=330402652647&ssPageName=STRK:MESELX:IT
he looks great in any grade...you may want to think about mid grades, rather than PSA 8's and 9's depending on your budget...