Reports had previously suggested the Baggies striker could be on the market for that valuation, with Tottenham linked with a move for the 21-year-old.
The Leeds striker traded Yorkshire for west London in an £11 million move this summer - and the West Brom boss feels that, if a move from Leeds United to Fulham can see such a high figure involved, Berahino will only be available for a lot more than £15m.
“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 told reporters.
“I would be absolutely astonished if anyone could sign Saido from us for £15m - Ross McCormack went for £11m, Championship to Championship.
“£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."