cheap, on the order of pennies. Microprocessors can get built into just about anything with almost negligible cost. And it's not just about "computing" capability. Cheap microprocessors are improving the experiences of everything from appliances to car dashboards.
When combined with cheap, plentiful bandwidth, you don't even need to embed the processor into the device. You can "outsource" the computing to servers in the cloud. Those computers can be far more powerful than what you can stuff into a small cheap portable device. Google is pushing this approach to the maximum with its Chromebooks, laptops that have just screens and wireless broadband, relying entirely on cloud processing for functionality. While not fully practical today, they point to a possible future scenario of all computing happening "off device."