Is this on a temporary work permit (such as HB-1), or do they apply for an employment based green card?
That, for me, would make a difference. As with the first one, you're tied to the employer for as long as you would like to stay in the US (or as long as they think you're useful to them). With a green card, you can move on to greener pastures.
What do they offer on top of that? Pension? Full benefits for you and the family (what is the deductible?)?
Factoring in the moving cost/visa cost into an annual wage is ridiculous, as this is only a one time cost (and illegal to charge the employee for that), while your wage goes over years and years (hopefully).
Permanent Resident in Ontario since 2010 * Canadian Citizen since 2016 * Winner of the DV-2017