OMG it is very very very simple
It means the rare minerals with the high tt values like Ruga thats worth ya know 1000% will only be found by skilled people. So if you are a newb there is like no chance you will find Gold, platinum, kanerium, dianium, langotz, tridenite, maganite, rugaritz, alferix, valurite, xeremite.
It does not mean you will loose more money
It means the mining system and skills actually have a point and make some sort of sense. wow what a concept.