For the players in the $3-4 mil AAV range and beyond, this is moderately small potatoes compared to the value that a playoff-tested player brings to the table. Yeah, an extra $90K for playing all four rounds and losing the Cup doesn't hurt - but if you're a player who breaks out, particularly in the playoffs, your next contract is going to be good. You can't compare $90K to a bump of $0.5 mil per year over a 5-6 year contract.
Even though the $150K bump for winning it all means proportionately more to the $550K rookies, the fact that they were active on a team that won the Cup means even more.