The 21-year-old has already netted six times in all competitions for the Baggies this season as a number of Premier League clubs reportedly weigh up January bids.
However, speaking to Sky Sports News, Irvine advised potential bidders to table offers in excess of £15m to get the club's attention.
"I would be absolutely astonished if anyone could sign Saido from us for £15m. You look at some of the fees going around in the transfer market that's just been, everybody seems to start at £7m," he said.
"Ross McCormack went for £11m Championship to Championship. What the right figure is I have absolutely no idea and I wouldn't make the decision as far as that was concerned.
"But £15m doesn't sound like a lot of money for a talented, young, English player with great potential who is playing really, really well in the Premier League at the moment and who is scoring goals. It would have to be higher than that."
Berahino, who joined the club as an 11-year-old, is contracted to West Brom until 2017.