Those tracks are a spot expensive.
Ebay and Bricklink are a good source that i've used in the past.
I have a lot of these;http://www.bricklink.com/catalogItem.asp?P=57518
from technic sets, they are a bit big for all but the largest vehicles though.
These hit the sweet spot for me;http://www.bricklink.com/catalogItem.asp?P=3873
but only have a few
these are a bit thin but can be doubled up to good effect; (£0.05pp)http://www.bricklink.com/catalogItem.asp?P=3711
[prices are listed as the lowest price with decent stocks, prices vary by colour]
I'm tempted to buy a bunch of tracks and get back into building, make some tanks or something.
"some people are like slinkies there really good for nothing, but they still bring a smile to your face when you push them down a flight of stairs"
"Triangalism! What's the fuckin' point!"