Ordered 20 Pro Micro's from Aliexpress
These were $35 for 10, with free shipping. Ordered on 3/5 and received 3/27. Three weeks in transit.
These did not have any Arduino sketch preloaded. Usually they have the blink sketch preloaded. I programmed all of them with my modified blink sketch (blinks faster than normal so I can tell which ones have been reprogrammed.)
One was DOA. It was recognized as a serial port and would reset when programming, but would time out while being written to. So total cost is $3.69 each for 19, after factoring in the dead one.