It is very unlikely that Bayern Munich will agree to such an offer and I think even if there is a valid source who says this, then it is clear that Bayern Munich will choose to look for another striker in the summer. The 180 million euro fee is inappropriate for a player who wants to be 30 years old and Harry Kane is more deserving of around 80 million euros.
Spurs are very good at taking advantage of the current situation and Spurs seem to benefit greatly from the two options available, for example Harry Kane will stay profitable because he has a top-class striker and even if he is sold he will still be profitable in terms of the money he gets.
180 Million Euros as a transfer fee are totally unrealistic in my opinion and so far i have not read a single news or rumor, that has stated this number. As you already said, Harry Kane is 30 years old already and he also only has 1 year worth of contract left at Tottenham. So if the Spurs want to get a transfer fee for him, they should be careful and don't demand to much for him because if no club is buying him now, he will probably leave the club after the next season for free, if Kane wants to leave Tottenham of course.
I also think that a reasonable transfer fee would be around 80 M€. That is already a huge amount of money for a 30 year old player, because the buying club can probably not resell him again in a few years.