That's pretty much the correct approach for very quickly and very roughly guesstimating a future value. In this case, and given these suppositions, you are correct, but that would be some 7 years following the commencement of production. These are very big "ifs", but the very reasons why early stage exploration stocks are so attractive to knowledgable speculators.
Frankly, I would expect LBSR to sell out long before then - maybe following Phase I drilling -, but I hope they would retain a royaly interest in the project in order to secure a rewarding income stream far into the future.
Why would LBSR want to sell out early? To use those funds to begin other projects that could well have the company's valuation at multiples of what it would be had they waited for full valuation to be realized at Hay Mountain.
Keep in mind that LBSR has many targets, and they are both costly and a liability without drills being at work upon them. ...got'a keep moving foward on these, or they can be lost.
All we know for now is that LBSR is studying what seems to be a monster of an intrusive that has all the hallmarks of a rich copper porphyry similar to what was mined at Bisbee by a dozen or more companies for nearly a hundred years.
Hope this helps.
VP