Measuring torque on something like a car requires that the "spikes" and average values be understood. Torque can range from very small to very large values rapidly. Do these values need to be recorded? Do they need to control or trigger some other device? The cheapest "sensor" I can think of is a shear pin. Such pins (like those used on lawn mowers to prevent crackshaft damage) give an indication of maximum torque up to the point when they shear into two pieces...
Do you need to know individual wheel torques? If not, measuring axle housing position could give you general torque, or engine/transaxle position on front wheel drive. I have seen something similar on older helicopter engines. Kind of crude, but may be what you need? Pay heed to previous response when considering this option. Does it need to work in snow or other types of sticky stuff? Are you really concerned with actual torque, or accel/decel of the wheel in question?
There are a lot of ways to measure torque at the wheels and some are very cheap; but, I can't tell why you want to measure this and when. That would allow someone to answer better. A used DC generator could be 'borrowed' for a measurment and this would be sure nuf be cheap. You are talking a couple of hundred foot-pounds so cheap in this case may be very high '$200 or so'. Of course if one has engine speed (RPM) and vehicle weight (lbs) and then measures acceration (g) with a poor man's dyno using a ball point pen and some wire and spring with a protractor, you could calculate pretty close. You could also buy a dash mounted meter that uses no connections but the cigerette lighter and read the display. The VC-200 by vericom is $200 and displays h.p. and torque and vehicle speed if you input engine speed. For fun, if its a one time measurement, you could do some cool measurements using a tree and a load cell that would allow you to calculate torque. That's pretty cheap.
