Looks like we are attracting lots of $$$ to build a mine. How do...

Looks like we are attracting lots of $$$ to build a mine. How do the long term economics stand-up?

Having a look at https://www.ga.gov.au/scientific-topics/minerals/mineral-resources-and-advice/australian-resource-reviews/rare-earth-elements

Lynas' Mount Weld Reserve : "The in-pit Proved Ore Reserve of 14.1 Mt @ 8.8% TREO had 20 200 ppm Nd₂O₃+Pr₆O₁₁, 300 ppm Dy₂O₃, 21 200 ppm La₂O₃ and 41 560 ppm CeO₂. The grade of the in-pit Probable Ore Reserve of 5.1 Mt was slightly lower at 7.7% TREO with 17 500 ppm Nd₂O₃+Pr₆O₁₁, 430 ppm Dy₂O₃, 17 800 ppm La₂O₃ and 35 630 ppm CeO₂."

Hastings Yanbigana : "In January 2019, Hastings released an updated Ore Reserve estimate that was 34% higher than that of July 2018¹³³. The new Probable Ore Reserve was reported as 10.35 Mt @ 1.22% TREO, which included 0.43% Nd₂O₃+Pr₆O₁₁.

Back in November - the chairman pointed out that TREO isn't everything and was quoted here https://investorinsight.com.au/hastings-knocks-yangibana-treo-out-of-the-rare-earths-ballpark/ :
“While the average head grades at Simon’s Find may be lower than at Yangibana’s other deposits, what is important and makes this deposit such a stand-out – in global terms – are the high levels of neodymium and praseodymium,”

The article adds comments from a Cannacord Analyst:
“A rare beast: low cap-ex, advanced rare earth opportunity in Australia,” Canaccord analyst Reg Spencer titled his initiating note to clients this week.Spencer noted the industry high NdPr-to-TREO ratio at Yangibana, “a key feature of the project … (which) … results in a higher rare earths basket price versus peers and improved operating margins and project economics”.“Our research suggests that Yangibana is the only greenfield, ex-China light rare earths development project capable of achieving production by 2023, a period when we expect supply shortfalls to appear in the NdPr market,” Spencer told clients.

Our overall NdPr ratio is 0.43%, c/f Mount Weld (probable) at 2.02%

How does our NdPr ratio compare to other Australian and global green-field projects?

Arafura's Nolan Reserve estimates are 29.5 Mt @2.9% TREO, of which 26% contain Nd2O3+Pr6O11 (which suggests a NdPr of 0.75%) - https://www.arultd.com/projects/nolans.html

Do we really have a quality ore-body with low cap-ex? Or are people just getting over-excited?

What am I missing here? Is Hastings project shallower than Arafura's?

Happy to be educated by all the geos and mining experts here.