The 19-year-old England goalkeeper is being chased by several teams, most notably Liverpool, who are understood to have already been in talks with the Midlands outfit.
Blues rejected a £6million bid from Southampton for Butland in the summer, but acting chairman Peter Pannu has admitted the cash-strapped club may not be able to resist such temptations next month as they bid to ease their increasing financial struggles.
"I can't say that we are in a very wonderful situation, I would be lying if I said that," Pannu told the Birmingham Mail.
"This is a very tricky question (player sales). What I can say is that - and I might be blasted for this by the fans - but no-one is for sale and everyone is available. As at any club.
"Give me a £15m offer for Jack Butland, can I say no?
"I have rejected £6m from Southampton (in the summer) but I rejected it when our finances were okay.
"As the time is ticking, I might not be able to reject it if I get something similar.
"I do have a responsibility to keep the club running.
"My top priority now - and if I do offend anyone, I care not - is to make sure this clubs stays afloat."
Butland is not the only player facing a possible exit, with a handful of other high earners troubling Birmingham's wage bill, most notably Nikola Zigic's £50,000-plus a week wages.
Pannu has been exploring the potential for bringing in new owners or finding investment in the club for some time.
The board of Birmingham International Holdings Limited (BIHL), City's parent company, announced late last month they were in talks with two parties from Hong Kong and one from the UK - Gianni Paladini's Italian-backed consortium.
They were at an advanced stage in discussions with one of the Hong Kong bidders - which has now fallen through.
Providing an update on the situation, Pannu said: "It is no secret that there are two parties in Hong Kong that we have been dealing with.
"The fans also know that my preferred party, which was reported in the media, the Charles Chan and SMEG group, unfortunately did not transpire.
"But we still have another very big party we are dealing with in Hong Kong."
Pannu also revealed he continues to be in discussions with Paladini's consortium and met a member of the bid for talks recently, although he is demanding greater clarity on those behind the offer and their plans.