As far as I know, the release clause is around €58m. But Bilbao should ask a bigger amount of money. If Barcelona wants to pay lower than €58m, I think Bilbao will reject it. It is true that Barcelona probably still have a problem with their financial although they won 2 major trophies last season. Moreover, Barcelona needs money to build their defense line, too. It is rumored that some defenders leaving Barcelona during the transfer windows.
The release clause must be paid immediately if Barcelona intends to recruit Nico Williams but to some extent Barcelona itself has not been able to.
It seems like this will be a failed transfer because I doubt Barcelona can meet the release clause fee with a slightly higher price, although Barcelona's interest in Nico Williams is still quite high.
Winning two trophies does not get Barcelona out of financial trouble and on the contrary they still have to pay such high salaries for several players.
Not to mention talking about the defense line which they should also think about and if several mainstay defenders also leave then the team's condition will not be good next season.