Why is NEST worth a pi-billion?

Question

Google

Dobra Corporation recently bought NEST (a thermostat and a smoke detector - just two products) for $3.2 billion ($3.14159265359 to be exact).
The question is, why so many? What in a project with about 200 employees and only two products allowed to receive such an amount?
I admit that the reasons are as follows:
1) Team (ex-Apple);
2) Innovation;
3) User friendly.
But all the same, this does not pull on 3.2 billion, which means there are some other reasons. Maybe someone knows?
Thank you!

Answer 1

The team (in the case of C-level) is good.
The volume of the market seems to me not so large, although it has potential.
But what about patents? Is there information on them somewhere?