Berahino has made a blistering start to the 2014-15 Premier League season, scoring five goals in seven matches for West Brom.
The England U21 international striker's form has not gone unnoticed, with Tottenham, Chelsea, Arsenal and Everton rumoured to be interested in his services.
However, West Brom coach Irvine warned potential suitors they must splash the cash if they to prise Berahino away from The Hawthorns.
"I wouldn't want to lose him but if he keeps on making the progress he is making then we will probably lose him one day," Irvine said ahead of Monday's clash with Manchester United.
"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.
"Ross McCormack went for £11m Championship to Championship (Leeds to Fulham). 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.
"I am desperate for him to play really well and if that means other clubs come and start knocking on the door then the club will make a decision on whether these clubs are making the right kind of offers or not.
"If Gareth Bale can be prised away from Tottenham I think it means every player has got his price."
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