Where's me calculator?
I got the numbers rong last time I tried. Wish me luck.
Pay up front: $830.
Pay monthly: the suppliers have their $850 after 17 months, and then you carry on paying them $50/month.
No wonder the suppliers like the concept.
Mind you, this is how Pipex kickstarted the UK mass market broadband scene almost a decade and a half ago. Hide the upfront installation costs in the monthly rental, and then carry on charging the same amount after the upfront costs are paid off. It worked back then.
Not convinced it would work today. See e.g. SIM only phone deals. People have wised up.