Buying back something you once owned, for a hefty mark up doesn't make anyone happy.
They are not buying back the property they once owned, they are paying for the exploration on the property. That is precisely why they are paying a multiple of the cost of exploration in order to earn back. The property alone had very little value. Now it has a substantial value.
What do you think is the goal of entering one of these contracts in the first place? Clearly they are hoping that something very large and valuable will be proven up. Do you think they would have been happier if we had found nothing and they were left with claims that were proven to be valueless?
All they have to pay for is the cost of the exploration and then they get their 75%. The further 3X that they have to spend in costs goes towards building the mine and that they would have to do anyway no matter who explored it. It's a very simple equation for Teck: do they think this property is worth the cost of the exploration?
Teck saves massive amounts of money by not exploring themselves every potential claim they make. They only have to pay for the successful ventures, not the highly speculative. I'm sure this policy is working out very well for Teck and their shareholders.