Reports have suggested Arsenal are ready to make a £14million bid for the 24-year-old.
Cahill joined Bolton in a £5million deal from Aston Villa two years ago.
Coyle said: “Gary could play for any Premier League club. If someone offers £30m, you’d probably say that is fair.
“He is at the top level and that is why it would have to be something like that. It would be wrong if we stood in his way.”
