Are salaries lower in Europe? If anything I would say his salary is low for his level of experience. He is former CEO of Chevron mining, MolyCorp and Largo receiving 400K? Thats peanuts for his level of experience. I know a lot of people making 400K a year with only a fraction of his responsibilities and they certainly aren't building a billion dollar project.
Having said that, this article from Mining.com gives a better idea of the norms for both junior and major mining company.
" the average chief executive officer of a junior mining company earned a salary of $297,000 and a reasonable bonus of $387,000." Average salary plus bonus was $694,000.