The last time this came up it was the usual EBay hassle of scams. Whether it is this time, difficult to say without checking the seller ID and history. The seller for the last one had been banned by EBay.
However I strongly suspect this is a blagged copy. If its in a standard CD jewelcase it certainly is. I would check quickly on the seller history - carefully - and do a chargeback via PayPal - the Community Forums there will help on the process. There is no formal outlet for Civ IV on EBay therefore anyone selling multiple copies at significantly reduced retail price has to be suspect, particularly the Civ IV Russian scam - its happened many times.
Your choice, but I would check carefully and quickly if you are to get money back from PayPal. If it was Western Union, vertually no chance of refund.
Regards
Zy