Matuidi has long been linked with a switch away from Stade Geoffroy-Guichard, with Arsenal strongly mooted as an interested party while Liverpool have also been mentioned.
The 24-year-old has previously hinted he would consider a move to England, conceding he desires to play at a side who have qualified for the UEFA Champions League.
"The right fee is €15million (£13.2m). We will not discuss anything lower," Romeyer told The Progress.
Romeyer also criticised Paris Saint-Germain following allegations the club approached Matuidi before speaking with St Etienne.
"The rule is that you contact the club to which he belongs before the player himself. Paris does things backwards," he said.