You've set your cost guidelines a bit low....for new stuff and (I assume) two riders. Probably the cheapest you will find is a Chatterbox with helmet speakers and mic. It can be mounted on the side of your helmet or remotely with a cable to your helmet. Reliable range is a mile or so in open areas...less in the city.
Most of the comm units have voice activation, but they are tricky to get working right as engine and wind noise tends to trip them. I gave up and just use push-to-talk.
My setup has a Zumo GPS and Chatterbox mounted on a ram mount connected to the helmet with a cable. The Zumo has XM radio and MP3 which turned low I think is safe enough.

Some states have restrictions on the use of speakers in helmets.....might want to check that.
Jim