Selanne is a terrible comparison, his career trajectory was extremely volatile. In his last 5 years before he started to take discounts he was ebbing and flowing from being well over 100pts to only around 60. It was really hard to peg what type of season he'd have.
His first discount wasn't really much by choice, it was coming off a horrendous and injury plagued year in COL where he put up only 32 pts in 76GP. Safe to say that at the time it was considered more of a low risk-high reward contract as it was very much unclear if he was on the steep decline or not. He was coming off of a third knee surgery and I think a lot of people assumed he might just be cooked. From there I'll grant you he took well under market value one year deals, but there was a reason. Any ideas? Buller? Buller? Ah yes... he wanted to win at least one Cup. He wasn't just taking under market deals for shits and gigs, it was to win a Cup. Do you think it's not at all odd that after that Cup he started to sign contracts for more money, including one for $4.5 at the age of 42?
I also think people lose sight of the fact that players purposefully don't take stupidly under market deals on purpose because it legitimately tanks contract negotiations for their peers. NHL contracts and salary arbitration use player comps to gauge "fair price". When you take significantly below market value you hurt your fellow player who might be looking for his first big UFA contract or arbitration pay out.