The Reds have made the first significant move of the winter transfer window after agreeing a deal with Southampton to make Van Dijk the world's most expensive defender.
Eighteen months ago, Klopp took aim at United for their then world record deal for Paul Pogba.
Asked about Van Dijk's move at his press conference on Friday, Mourinho said: "I think the one to speak about it in a specific way has to be Jurgen. If I was one of you I would ask him about his comments about one year ago (when Pogba signed).
"Not speaking specifically about (the Van Dijk) case because in Liverpool they do what they want, and I am nobody to comment about what they do, (but) the reality is if they think the player is the right player for them, and they really want the player, they pay this amount or they don't have the player. That's the way the market is.
"When we compare now the amount of money that certain managers and we try to compare that...not even with 10 years ago, (with) three years ago, it's to compare the impossible.
"Now you are going to say Virgil van Dijk is the most expensive defender in the history of football. Was he better than (Paolo) Maldini, (Giuseppe) Bergomi or (Rio) Ferdinand? You cannot say that.
"It's just the way the market is. You pay or you don't pay. If you pay, you pay a crazy amount of money but if you don't, you don't have the player. It's as simple as that.
"No criticism at all about what Liverpool did. It's just the way it is."