Shaun:

If its really that expensive, I'm glad I don't live there.
I just checked the wire man catalog here, and he has twin lead for $0.33 per 
foot, or 300 ohm window line for $0.25 per foot.

Howard is right, coax is certainly not optimal.

How about making your own balanced line.  #18 wire, and cut up those plastic 
hangers to make spacers.
If you like, I'll dig up the formula for spacing v impedance.