PP White Wyrms can have up to 760 str. The real "good" ones have more than 750 str, in order to get maximum damage out of it, if you have skilled it with chivalry and armor ignore. Furthermore most ppl look at its cold resist, too. The lower it is, the better it is for a "normal" resists balancing. So a cold resist at 88 is not that, what ppl are looking for normally, but it should sell for more than 100m. If it is a "real" very old one, especially from 1998, you should give it a command like "all follow me" and hear what sound it does after you gave that command. If it roars like a normal dragon, then it is very very expensive, no matter what str. and resists it has. If it "grunts" after you gave a command, its a normal prepatch one.