The promised money should see full use within the next two years. Apple has promised to pour any leftover money back into other projects over the next five years.

Cook characterized the plan as a recognition of its "profound civic responsibility" to its hometown, and noted that lower-cost housing meant "stability and dignity, opportunity and pride." The current path was "unsustainable," the executive said.

Of course, there are pragmatic reasons for the investment as well. The more people leave the area to avoid its soaring housing costs (roughly 30,000 people left San Francisco just between April and June), the fewer recruits Apple has. Those prices also force Apple to increase salaries and otherwise spend on perks to keep people from leaving. What the company spends now it might recoup by accessing a wider pool of talent and keeping its employment costs in check. There's also the simple matter of earning goodwill with politicians -- it may have an easier time forwarding its agendas if it improves California's communities.