The most attractive resource on the moon will be the one that most reduces the costs to taxpayers of proposed moon missions. Water seems the most likely candidate.
Any mining on the moon must contend with extreme pre-investment and operating costs that bear no real relationship to commodity prices. There is no prospect of viable mining to service commodity market demands or that can induce self-perpetuating commercial investment; transport costs alone are probably thousands of times too high for commercial viability.
Ultimately there is no separate moon economy and the primary attraction of in-situ resource utilisation is reducing costs to taxpayers of moon bases that have no commercial basis. As a cost reduction a thousand liters of water on the moon could be "valued" at many millions of US dollars but the on-Earth and on-moon pre-investments needed to deliver that thousand litres is difficult to quantify.
I think we can assume it would be an extraordinarily expensive undertaking, made more difficult for being unable to utilize any regular mining equipment that is mass manufactured as well as the extreme difficulties of sending heavy machinery to such a distant and extreme location.
We cannot know what it will cost or even how without doing it.