If Taumololo isn't already the best player in the nrl then he is easily the best young player in the game.
At 8 million ($800k a season) it is an absolute bargain. In 5 years time 800k may be cheap for an elite player, with Taumololo locked up already it could be an astute signing. Cowboys may have not been able to keep him any other way, and if the choice was take a 10 year gamble or lose him I'd take the 10 year gamble any day, Taumololo is that good and that important to them. At the very least I can't see Taumololo failing over the next few years, giving you a few years to make other options. If he does get seriously injured then I think it'd be easy to pursuade him to medically retire with so much money promised.