Hello,
Looking at your project, it appears very similar to jobs I have successfully completed in the past. I've utilized off-the-shelf transmitted modules, that are already FCC-approved, which will drastically cut down any certifications you may need to undergo. Additionally, I've seen ranges in excess of 4 miles, while not bringing the cost of the device over $50. I'd expect, based on preliminary research, past experience, and contingent of the cost of the GPRS modem, for the module to cost around $100-150 in production quantity.
We will have to further discuss the requirements in terms of the software for the end-user, which may affect the bid slightly. I'm additionally open to working on at an hourly rate if that is more convenient for you.
Feel free to discuss this bid with me further if you wish. I am available via phone, email, IM and skype. I am based in the Northeastern US, where all work will be completed.