You're comparing one component to a complete product.
At a minimum you'd need to add a TTL-to-RS232 converter, wiring, connectors, and I believe a proprietary "MFi" chip from Apple is required to use protocols other than the ones blessed by Apple (and surprise, the serial port profile isn't one of them)
Plus the prices I'm seeing right now show the cable is $59.00 and the Bluetooth chip is $59.95.
At a minimum you'd need to add a TTL-to-RS232 converter, wiring, connectors, and I believe a proprietary "MFi" chip from Apple is required to use protocols other than the ones blessed by Apple (and surprise, the serial port profile isn't one of them)
Plus the prices I'm seeing right now show the cable is $59.00 and the Bluetooth chip is $59.95.