He's pitching it as being basically break even, when electricity costs are factored in. My guess is an awful lot of people can afford this, especially for new construction.
I think this is key - often the pitch that "sure, it's expensive up front but will save you money in the long run" falls on deaf ears when people don't have the disposable income to immediately absorb that large up front cost, but when you're buying a house in most cases you're already taking out a large loan to finance a big up-front cost.
You're aware, of course, that SolarCity's entire business model is leasing solar panels back to consumers with no up-front costs, and a net savings, right?
Okay, so what they do is install the panels on your house for "free" (or some rough approximation thereof). They claim the Federal (and perhaps state?) tax credits on your behalf, and then "lease" the panels back to you. I believe you pay a set monthly fee and are also responsible for your electric bill, though of course the system is sized so as to minimize the bill that you pay the utility. They also maintain the system (cleaning, repairing broken parts, etc).
The advantage, of course, is the 0/low upfront costs.
Whether or not this model works for the roof tile system is another question entirely. Of course, the bill would be much larger, but the tax credit might be larger as well.
I'm not sure how they handle a circumstance in which your income causes your tax credit to be phased out. Likely there's fine print where you have to pony up extra money.
BTW this is now being shifted. They are allocating less and less to outright leasing. Musk said he expects in two years that all of their sales will be either loans by banks or outright full purchases and the leasing business going away.
I think this is key - often the pitch that "sure, it's expensive up front but will save you money in the long run" falls on deaf ears when people don't have the disposable income to immediately absorb that large up front cost, but when you're buying a house in most cases you're already taking out a large loan to finance a big up-front cost.