I was told they had "Letters of Support" that validated the use of $8,500 in the 43-101. A Letter of Intent would be a step above that for sure. We know that RPA is a conservative outfit so we know they HAD to have support, solid support, for that number.
You raise a good point though, what if the PEA is released and it does not SPECIFICAALY note how the selling price was supported? Will the market yawn once again? I would think AE knows he has to show some proof of that numnber and perhaps he is handcuffed by NDA's on that score.
But even analysts will want to see public disclosure of the price used, given a low cost mining number the selling price will be the LAST possible contentious issue for naysayers.
And perhaps your very last comment is true - this will be the news beofre the PEA. I hope so because I cannot see any other news of significance having a stock price impact other than the PEA itself.