I think Caps have two key adventages over other teams:
1) They can offer an 8-year deal while others only 7-year.
2) Under equal conditions Carlson is gonna choose Caps, so other teams have to offer more than Washington.
So, if Caps offered Carlson $60M (7.5x8), other teams would have to offer $63+ (it's more than $9M per year). Do you know the team that would offer him at least 9x7 contract, especially among contenders? Actually, I doubt that other teams (the ones Carlson would be willing to sign with) would/could pay him $8.5+ either, so I believe Caps and JC could agree on 7x8 contract. Anyway, Carlson's new contract with Caps shouldn't be more than $7.5M per year IMO.