Megaman The Wily Wars for €6 ... a megadeal ??

Yesterday I found MegaMan The Wily Wars (European version) for Megadrive/genesis for €6 ($6.5). There wasn't a manual with it, but the game and the box are in good condition so I guess its still a good deal. I looked for it on ebay and couldn't found even 1 single copy for sale so am I correct if I say it's pretty rare ? Does somebody here know what the value of this game could be as you are all experts :)
Seems like quite a good deal to me, I haven't spotted that game out in the wild ever. I bet you can sell it to a collector for about 15-20 euros.