You think wrong.
Extract from speedguide.net
"Below is a breakdown of actual real-life average speeds you can expect from wireless routers within a reasonable distance, with low interference and small number of simultaneous clients:
802.11b - 2-3 Mbps downstream, up to 5-6 Mbps with some vendor-specific extensions.
802.11g - ~20 Mbps downstream
802.11n - 40-50 Mbps typical, varying greatly depending on configuration, whether it is mixed or N-only network, the number of bonded channels, etc. Specifying a channel, and using 40MHz channels can help achieve 70-80Mbps with some newer routers. Up to 100 Mbps achievable with more expensive commercial equipment with 8x8 arrays, gigabit ports, etc.
802.11ac - 100+ Mbps typical, higher speeds (300+ Mbps) possible over short distances without many obstacles, with newer generation 802.11ac routers, and client adapters capable of multiple streams."
