Wirelessly communicate between two Arduinos without router I want to "connect" two Arduinos, without using wires. The range is ~0.2 miles (300 meters). Using Google, I saw too many options.

The idea is to build something like a beacon, so the bandwidth can be small. I want to send 32 or 64 bits/second of data (32 bits for the application + 32 bits for checksum if the module does not guarantee consistency of data). 
The communication between Arduinos is bi-directional, and I'm looking for something cheaper than 50 US dollars per module.

Can I use a serial WiFi module for this, without using a router? Do you recommend a 2.4GHz module? Or a RF module?
I can highly recommend these cheap little 433Mhz radios.  You can get them on amazon, ebay, etc. and they work pretty well for me. Your distances are a bit longer than my situation but I have to go through several walls.