I don't believe that the FF sensors cost dramatically more to make than 1.6 crop sensors. They use the difference to allow them to sell cameras at a lower price point to 95% of the people buying cameras without undercutting the prices on their own FF models.
You would believe wrong then.
A FF sensor has approximately 2.6x the surface area, so they only get about 1/3 as many on a wafer.
Because of the increased surface area there is an increased risk of flaws, but not a 2.6x increase, a 6.9x increase. (actually 6.9x (square of the difference) sounds a little high, so don't quote me on that. I do know it's not linear though.)
There is also the reduced volumes vs. APS-C, especially taking into account for the 18MP sensor that has made it into seemingly half the APS-C bearing line.
Add those all together, and you get massive cost increases.
As to your second point (unquoted for brevity)...
Even an APS-C sensor is larger (up to 2x) than the latest 6 & 8 core Intel processors. Have you priced out an 8 core Xeon lately? They start north of $1k in bulk. And even the newest 10 core E7 processors are almost half the size of a FF sensor, and they start at about $2500.
Sensor vs. CPU isn't an entirely fair comparison though. Processors are several orders of magnitude more complicated, and expensive to fab. They're also more sensitive to flaws.
So I guess my takeaway point is... Things are more complicated than you think.