I think the market for tools now is such that one gets what one pays for in terms of reliability, accuracy and quality. I'd suggest paying a little bit extra for a higher quality brand such as Craftsman or Husky Pro that will have better longevity. The potential problem with torque wrenches is the tension spring and how long it maintains its elasticity and repeatable measurements. You wouldn't know if this was beginning to fail and giving you innaccurate torque values. I personally wouldn't put much trust in a $10 torque wrench for long term use.
Why is this important? Well firstly, it helps stop your wheels falling off at the most inoppotune moments, and secondly, inconsistent torque values around your hub can lead to warped discs and wheel vibration.