Nats revenue is over 350 million. They have no real payroll to speak of. They can absolutely afford to match whatever offer the Phillies have.
Considering the Nats current payroll they could afford to add Soto. But there's a reason Harper, Turner, Schwarber are signed by the Phillies and not the Nats. The Phillies are getting $64 million more in TV revenue that pays their salaries, money the Nats don't get for their TV deal. That's a big reason why the Dodgers and Yankees of the world can sign these big contracts.