I found this business case for installing wireless LANs; even though a little dated it is approximately where we are now regarding costs.

My network of four computers cost me $370 for a totally wireless network. This is compared to my first wired network buying a network card per computer, wires, and wall fittings, router, in total, $1,500. Every small business cannot afford to do anything other than a wireless LAN.

AND while we are talking about wireless LANs, maybe you are having new difficulty with your wireless LAN -- well here is the site you need -- 5 Techniques for troubleshooting your wireless LAN.