Wireless traffic in general is fairly bursty, and it is half duplex, so it takes much more to sustain a gigabit of traffic, for example. In addition, dense wireless networks have a fair amount of contention, so it takes a lot more wireless users to drive the same amount of traffic that wired users would. Retries typically would reduce the throughput of traffic.
With that being said, do you have any bandwidth contracts configured? Are all of your access points on gigabit Ethernet ports?