The reason I think it has to do with Tech is, when you scout a planet you'll see something like 900/45. 900 CO/45 RO per hour. But then when you colonize or outpost it, it goes down to like 900/8. I have the first Tech level of Rare Material Gathering, and I would put money on it that my RO output would increase up to a max of 45 on said planet if I maxed out that tech.