"if one has no idea about the underlying value of a company, the...

"if one has no idea about the underlying value of a company, the price information will actually be useless."

Nathan,

I agree with you there.
But the problem is that we can not always value a company's assets based on the information that directors have given us.

If we are taking of tangible assets, such as plant and equipment, then directors tend to overstate its value.
So, too, if the valuations used for plant were pre-GFC, then that is of little use to us, as its value, also, has plunged along with the commodity that the company was mining.

There again, many of the small mining companies don't actually own any plant, what so ever. They either lease it or use sub-contractors to do the actual work.
So then we only really need to worry about what the value of the resource in the ground is worth. What is costs to mine, process, and the logistics to get the commodity to market.

And this information is not always made clear by directors. They will gladly tells us how wonderful their patch of dirt is. But not readily tell us of how much per tonne it's going to cost to get it to market.