Mark pays a heavy price for his cowardice, his inability to face up to reality and do the mature, adult thing in a difficult and tense situation. I feel that Mark might be paying this price for the rest of his life, but Meredith pays a heavier price for her involvement with Mark.
Bentley talks admirably and openly about the impact the operation had on his mental health, and the lack of aftercare and support that he got from the force. One of the most psychologically fascinating parts of Operation Julie is how Bentley manages not just his dual identity, but how his experiences in Wales, and getting closer to the people who were involved in the making and selling of LSD changed him as a person. It feels obvious that Bentley could not finish the job and simply go back to who he was before, he needed to find a new self, and that was no easy feet.