Not many games are rare.
Expensive games are many times not really rare because there are always enough of them on Ebay.
I have Beggear Prince for the MegaDrive, the first print edition, only 600 of them released in 2006.
I do have some expensive games like Shenmue 2, Suikoden 2, Tales of Destiny 2, the Lunars, Brigandine and some others.
''Hadouken!''