Yes, I know. So?
Bayern is the financially most healthy club on this planet by far, not a single dime of debt and at the same time a huge enterprise with quite a bit of profit each year and gigantic revenue.
They would be able to meet the clause even without backing by Adidas or Audi (of course THEN they would have debt, quite a bit ofc), but the most likely case would be that Adidas would jump at the opportunity to bring Adidas sponsored Messi to an Adidas sponsored club, the biggest one in their country of origin in fact.
As I said, it's not gonna happen anyways, especially since Bayern always refused to pay ridiculous transfer fees (Martinez excluded maybe, he proved his worth however pretty fast), but claiming Bayern would not be able to afford him, seems a bit of a stretch.