I'm working on a project that requires wireless transmission and reception of data. I wonder what the best technology would be. It is not tons of data maybe not even a kilobyte. And the range should be +10 meters. At first I thought Bluetooth. It satisfies all the requirements but one, it is too expensive. Maybe there are some cheaper modules on the market but I don't know of any. There would be 3 components to my projects: repeaters, a transmitter (raspberry pi), and receivers (most likely operated by cheap PICs). I thought I could get IR down to ten bucks per receiver and maybe fifteen per repeater. If you could help me that would be great.
"Best" can mean "cheapest, at the expense of development time" -- it can also mean "easiest to get going quickly".
There are tons of low-cost ASK OOK transmitter/receivers out there. Heck, you can build a transmitter out of a transistor, a SAW resonator, and a few passives. Those are going to be really cheap, but you'll have to develop a simple communications protocol (those things will basically get you a virtual 'noisy' wire -- what you do with it is up to you). These are typically used for one-way communication, like garage door openers. You can buy modules for a buck or two each on eBay / aliexpress.
Next up, there are more intelligent transceivers, like the ChipCon / TI CC1101, which let you send and receive data at the packet level. Often, that's good enough, but you may need to implement a protocol on top of that if you want stateful connections, guaranteed delivery, et cetera. You can buy modules for $5-15.
And finally, there are off-the-shelf protocols, like ZigBee or Bluetooth LE. These do all the protocol for you, but can be complex to design around for cheap. Of course, many vendors would be more than happy to sell you pre-built / pre-programmed modules, but these usually provide only a basic serial profile (Series 1 XBee, many BTLE boards), which really doesn't get you much more than an OOK transmitter/receiver set. Great for PC / Smartphone interfacing, though!
I like the digital radio transceiver modules based on nRF24L01+ chips. I seem to remember you can get over 100 meters of range from them, at least using the low data speeds. And they're really cheap on eBay; e.g. the first search result I got was $4 for 4 modules. You'll just need to write (or find) software to use them. Note that they offer digital packetized data comms, not just an analogue link like some of those old-fashioned cheap radio modules that you can still find.