[popcornmix]

The above results show that Edimax EW-7822UAC could be used for playing BluRay video over wifi.

Looks promising. I'd have expected more degradation from the increased distance.

This tells me that there is something else in play here, maybe some sort of additional overhead, but I don't know.

There are two performance numbers used for a network link, bandwidth and latency.
iperf measures bandwidth and ping measures latency.

Wireless tends to have much worse latency than wired.
If a protocol blocks until messages get responses back, then latency can have a big effect on bandwidth achieved as the link is idle waiting for responses.