I'd speculate that its not just the average annual value, but possibly the term.
I imagine the Stars would strongly prefer a 1 year deal and certainly no more than 2, while Dobby, understandably, at his age and with his value never higher, wants to see if he can get 3 years and certainly wants at least 2.
I hope it works out, but both sides might have to amicably agree it just isn't the right fit. The Stars probably just can't provide neither the years nor the money. Maybe if the goalie market, with so many teams struggling with the salary cap, doesn't develop they find a way. Not holding my breath, though.
Hanging over all of this is the coming expansion draft. The Stars will have to expose a goaltender under contract for 2021-2022. Oettinger will be protected as a young player, and Bishop would have to waive his no movement clause.