We're going to pay whatever Dortmund ask us to pay.
The most financially vulnerable phase of football is over. All stakeholders got hit unexpectedly, now they'll plan for it better. Leagues, clubs and consequently footballers at the very top will adapt to the new state of football and quickly create a new bubble for their systems to function anticipating second and third waves of the virus over the next couple of years. The TV deals will not massively drop because they'll have increased coverage during social distancing and lockdowns, and will structure their payouts with more detailed ifs and buts. Corners will be cut in the wake of the new methods of functioning of clubs, and diverted to PR in terms of charity or support to deflect criticism of that bubble. Another Maguire will ask for a 30% cut to charity, another Rashford will drive a strong social cause. Germany, Italy, Spain, France and England all receive massive amounts of much needed taxes from this footballing bubble and would be reluctant to interfere unless things are really really bad. If the leagues and clubs are already practicing the policies recommended and football keeps morale high, why should they interfere?
The bottom line, in my opinion, is that this is the only time when clubs will be so badly hit with the imbalance between revenue and expenses, and hence this is the only window where it is really bad for clubs to spend big. By next season, clubs at the top (only at the top) will be in better financial shape again, and will be willing to pay more for top players. There are a handful clubs who can pay 100m for a player if their finances are functioning as usual, but there's only one Jadon Sancho with a year left on his contract.
If I were Dortmund, I would quote the usual price for him, fully expecting no one to meet it and happy if someone does. Next year, someone or the other will pay a fortune for him nonetheless after a bidding war - there's enough evidence to be sure that he's no one season wonder. Even if he has a poor season and it means the fee is 30m-40m lesser, it shows that they won't be lowballed and they would have recouped some of that loss in his performances nonetheless with another good league/CL run.
I'm sure the money people at United know this, and I'm sure Ed would be looking back at all the times we tried to negotiate for a top player but ended up paying premium at the end because we're still not in a position of strength yet. We either pay what they want, or we quit. And given the possible returns over the next decade from such a young prodigy and the insane balance he'll add to our squad straightaway, we will not quit.
There will be a lot of posturing over the transfer window, a lot of drama with United trying we can to lower that price, but in the end we'll pay what Dortmund ask, and we'll get Sancho.