According to (https://www.quora.com/How-much-does-it-cost-to-set-up-and-la...) it costs ~$80-$100 million per satellite to build, launch, and run. So that's ~$354-$443 billion for all the satellites. Let's call it $443.
Now, I pay ~$60/m for internet. That's $720/yr. If they want to recoup costs after 10 years, it'll take ~61.5 million subscribers.
For the U.S. alone, that'll probably never happen. But worldwide? Maybe. Though worldwide the price per subscribe will be less, often times substantially less.
On the other hand, SpaceX will have lots of operational discounts because its their own rockets, and they already have all the supply channels for building space tech. And maybe they aren't looking to payback in 10 years for this initial run; maybe they only want to break even so payback in 15 is good enough.
Just some numbers for thought.
P.S. Businesses unlucky enough to be in "rural" areas, aka most commercial business parks outside of tech cities, are in the unfortunate position of paying the local telephone company/AT&T/TimeWarner thousands per month for roughly dial-up speeds. SpaceX could charge the same but offer broadband speeds and get a nice chunk of business, methinks.