This month, Bayern coach Jupp Heynckes confirmed that talks had begun to bring Wagner to the Allianz Arena during the January transfer window as the Bundesliga champions attempt to provide support for Robert Lewandowski.
But as things stand, Rummenigge says he cannot guarantee that a deal to sign Wagner – who started his career at Bayern – will be agreed.
"It was clear Hoffenheim won't shoot low, but higher than we imagined regarding the transfer fee. I don't know if we reach an agreement. We are not ready to pay every prize," he said at a press event at the Bavarian environment department.
"We have to speak about that issue intensively with the coach. If he sees the necessity and we can reach a reasonable transfer fee, I won't exclude that."
Lewandowski has voiced his frustration this season at a lack of back-up in Bayern's striking ranks, and Rummenigge says others may be considered if a deal cannot be sorted for Wagner.
"For sure we discuss that, we don't speak exclusively about one case," he said.
"But he is a player who has interest. He has huge interests privately. His wife is living here, she expects her third child.
"I would say there are common interests between us and the player. So it's not too easy for Hoffenheim."
Rummenigge also addressed any potential concerns Germany international Wagner may have about switching clubs in January with a World Cup on the horizon next year.
He said: "If he does it, he'll have spoken to [Germany boss] Joachim Low and he'll have found an uncomplicated solution."