This is factually incorrect. To have wifi and BT support, you need a processor that is powerful enough to run a TCP/IP stack. In practice, that means an SOC that can run some version of embedded Linux. That's a far cry from a simple micro-controller that is just smart enough to monitor a handful of buttons and operate a 7-segment display.
The cost difference is measured in dollars, not pennies. On a device that costs $100 retail, $2 in manufacturing cost make a big difference to the bottom line of the manufacturer.