You are wrong. I am using Cobra to play and yesterday I have sold stolen cargo for 150K for full cargo hold.
As for black markets - there is no black market at Beagle 2 (Asselus Prime). There are black markets at Azeban, Chango, Freeport and Dahan. I did not check the new 3 stellar systems. And of course black market prices vary as the commodity market price. E.g. you will get more profit by selling gold at Dahan or Chango than at Freeport or Azeban. Way more 4.8K vs 3.6K.