long distance serial communication

hii...
i am working on a project where i need to transmit serial data over a long distance approx 2 miles...on twisted copper lines(2 wires)
can you offer suggestions on how it is possible...
i googled it and found out that there are many drivers and modems for this but with insanely high prices like a 1000$

please help me out i am really stuck against a wall here....

Its a Data acquisition system
i am using avr to measure temp humidity and power and tx it via uart to a PC
there will be many avrs joining 2 the pc... i am using only 2 wires tx and gnd
no feedback needed, the problem is...
the distance between avr and pc is approx 2 km