Assuming your signal quality is good, ie. not many or no retries, then pretty much 0 to 1 ms will be added to your ping. That's the wireless part anyway. If you see higher ping times due to a wireless device the one of two things is going on.
Your association from the AP to the card is poor, causing beacon and packet retries, or
the latency is introduced after the RF data transfer. Like the wired part of the device, SOHO router etc.. Microwaves are electromagnetic waves. Speed of light. At 18 miles pings from wireless device to wireless device are around 1-3 ms given a solid link. If you buy a wireless AP or router/AP combo and your pings go up, adjust your devices so you have a better AP/CLient association or start troubleshooting on the wired side.