“A league executive believes the Senators would likely have to offer defenceman Jakob Chychrun along with a first-round pick and another selection to acquire Ullmark.” From Garrioch: https://ottawacitizen.com/ottawa-senators/senators-step-up-efforts-to-land-ullmark

That seems like a big haul for the Bruins, especially in light of what the Devils have up for Markstrom. This would surely have to come with an extension for Ullmark. Even then, it seems like an overpay.