The Spaniard joined for just £2m last summer, and has scored 27 goals in 53 games for the Swans.
Laudrup, who previously managed in Spain, admitted that Michu's impact on the squad makes him one of his finest buys.
"I always try to get good deals for players," Laudrup told reporters. "Michu must be my best buy because of his importance and the impact on the squad.
"It's not only about goalscoring. He wants to win and can change a game in one second. We have seen what he is capable of, he can play up front or in behind and that's a very difficult position.
"He's a very important player for us and it's impossible to put a value on him."
Laudrup recently admitted that the striker could leave the club next season.