Rewards in this game make no sense. Many players would say that credits can be removed from the game. As you can easily earn 100M in an hour. And if you play for credits you can get everything you need in a day or two. Then you just go and buy whatever you want. And killing Thargoid scouts for 10K is a joke. I hope that FDev would reconsider the reward mechanics in 2019. Something they should have done years ago.
That has only been true in my since they added the new mining tools and certain minerals became selectively profitable. Prior to that, the highest my account ever got was about 180mil, and that was after MONTHS of hacking away at a mixture of exploration and local missions. It has been a painful process to get the ships I want, get them outfitted the way I want and get them engineered the way I want. Or, at least as close as you can out here in Colonia---where you cannot GET a lot of the A- or B-rated modules and get NONE of the unique items from the Empire, Federation or Alliance. So, you need to consider that not everyone has figured out the get-rich-quick schemes. As for Thargoids, as others have pointed out, going after the Scouts is much less about the money than it is about the Combat Rank and gaining a little bit of skill against Thargoids in general. I thoroughly enjoyed the skirmishes I got into with the Scouts and it helped me get Dangerous ranking in a couple of weeks (from Master). I can barely make a dent in my Combat Ranking now that I'm back in Colonia, even going to compromised nav beacons. So, I'm very much in favor of keeping the credit system in place and in FDev enhancing and fixing the issues with Thargoid challenges. I don't think they should change anything about the Scouts.