Controversial statement time: The Undertaker, whilst still a token attraction (predominantly for older fans) isn't the same kind of box office smash hit he once was.
Note the title of this piece. It's all about 'incredible' paydays, not necessarily negative ones, and whereas nobody should criticise WWE for keeping 'Taker on their books, it is true that he doesn't work often. Perhaps he's earned that right, although it is hard for anyone to justify a cool $2m per year when for so few dates.
In 2014, those 'limited dates' extended to exactly one match against Brock Lesnar at WrestleMania XXX. Keep in mind that $2m is the minimum The Undertaker earned for doing that too. He would've surely been handed a pay-per-view bonus on top of it, meaning he scooped quite the pretty penny for one date and one job to the all-conquering Lesnar.
Since then and post-streak, 'Taker's appeal has diminished a bit, certainly when it comes to 'Mania.