The Basque club are insistent that the midfielder will not be sold on the cheap, but the Roten boss stated that the Bavarians will not pay over the odds for the Spaniard
The Spain international has been linked with Bayern in recent weeks as the Bavarian giants look to bolster their squad after two trophyless seasons.
Athletic president Josu Urrutia has declared that the Estella-born player will not be allowed to leave for less than the clause set out in his contract, but Heynckes, who has coached the Basque club twice, insisted his current side will not overspend in order to land the versatile 23-year-old.
"It is not a secret that we have spoken with Javi Martinez's agents," he told TZ. "I have also spoken with Josu Urrutia, who played for me in my first stint at Athletic.
"I know how the Basques think. The fact that they insist on asking for the figure in his buy-out clause is also a political decision.
"Bayern will never pay that figure, that is for sure. There is always hope, but I am not sure that it will be easy to sign him."
Javi Martinez, who signed for Athletic from Osasuna 'B' in 2006, has a contract until 2016.