[colsandurz]

Not only that but APs usually have more antennas, which makes a huge difference. The antennas can also be spaced out more (for better diversity) and be physically larger (typically you get more gain the closer your antenna length is to the wavelength of the signal).

You can also have better analog RF components with more space (filters, LNAs, PAs, etc).

It's not necessarily true that the "advantage" of the AP is symmetric as well. The tx power is limited by FCC part 15 so the difference in tx power between AP and client is probably less than the difference in Rx sensitivity between the AP and client.

Even if the uplink and dowlink are symmetric, the traffic profiles are probably not - there's probably a lot more data going to the client.