Pereira has been the Baggies talisman ever since arriving from Sporting Lisbon in a £9million deal at the beginning of the 2019/20 campaign.
The 24-year-old shone in the Championship last season.
And he is now taking that form into the Premier League with the playmaker having scored nine goals and registered five assists despite Albion’s struggles.
A host of clubs are reportedly plotting a move for Pereira this summer – with Villa amongst the clubs being linked.
And Allardyce – whose future is also unclear – believes it will be hard for the forward to remain with the Baggies if they receive an acceptable offer for him.
“There’s a price for everybody, isn’t there – everybody has a price,” the 66-year-old said.
“Whatever price the club thinks Matheus is worth, if anybody goes above that then I would think it would be very difficult for him to say no. You wouldn’t know what Matheus is thinking after this season.
“Certainly in the latter part of the season when he’s proved himself to be more than comfortable at this level.
“We’ve got a lot of conclusions to come to – well the club has – on what the situation is.
“We’d like Matheus to stay but you don’t know what he’s thinking and you don’t know what other clubs are thinking after the way he’s performed.”
Meanwhile, Allardyce has been nominated for the manager of the month award for April.
But with Albion on the brink of relegation, the boss says the nomination means very little.
“It’s nice but it doesn’t give me much satisfaction,” said Allardyce who is up against Marcelo Bielsa, Steve Bruce and Ole Gunnar Solskjær for the honour.
“I’m just frustrated that there have been times when we’ve looked like we would turn things around but we haven’t.
“At least our consistent level of performance has been recognised because we haven’t had many losses in our last 11 games.”