Michu's Spain call-up means potential suitors will have to pay more than 30 million pounds for the striker, Swansea chairman Huw Jenkins has said.
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Following an injury to David Villa, the 27-year-old forward has been selected in Spain's squad for the first time as they prepare for World Cup qualifiers with Belarus and Georgia.
In December, Swans boss Michael Laudrup insisted Michu was worth 30 million pounds after his incredible start to life in the Premier League following his £2.2 million move from Rayo Vallecano.
Michu went on to score 22 goals in all competitions last season, and has already netted five times this term, and Jenkins said the price would now be even higher if anyone tried t prise him away from the Liberty Stadium.
"We've seen with Tottenham and Gareth Bale that every player has a price," he told the Daily Mail. "We are not in that bracket with Tottenham, but they sold a top player. We are realistic about that side of things.
"I would say Michael was about right with his valuation of Michu if you look at the current market, but this call-up enhances that further.
"We know we have a very talented player, and naturally we want to keep him."
Michu is tied to Swansea until 2016, having signed an extension to his contract in January, although it has been speculated that he could depart if Laudrup leaves the club next summer.
However, Jenkins said he has "never had a single phone call to express interest" in Michu, despite Liverpool and Arsenal reportedly monitoring his progress.
Michu, meanwhile, has said it is a "dream" to be included in Vicente Del Bosque's squad after discovering he had been selected while on the team bus back from Swansea's 2-0 defeat at Southampton on Sunday.
"Every Spanish footballer dreams of this and it's so difficult," he said. "Few people can wear the shirt of the best team in the world.
"Let's see if fortune is with me and I can play, although I'm already grateful to be called up. It's the maximum to which a footballer can aspire. The national team is the best in the world -- it's a privilege. I'm enjoying it like a kid."