help is there any cheap wireless method then RF for short distance?

I want to develop a project to transfer the data with very less cost. suggest me to select the cheap and short distance communication method. i tried RF 433 Mhz modules but i want to to use above 500 transmitters at different place to transfer the data for movable receiver. help me to choose the which technology ?

have a look at the Nordic RF devices
http://www.nordicsemi.com/eng/Products

BLE (Bluetooth Low Energy) modules can be had at a very low price (~USS25). I've been working with the BLE112 and BLE113 from Bluegiga, and I've been fairly happy with the results (just don't expect a high data rate).

It is hard to beat cheap 433 MHz RF-modules in cost, < S1/each.
Should it also be non RF technology do only sound and light remains as transceiver technologies.
IR-diodes of type used for TV remotes have similar cost but is limited to optical sight between transmitter and receiver.