Feng-GUI Attention analysis can serve you as a cost effective alternative to eye-tracking.
Of course, there are pros and cons for using eye-tracking.
Here are some good articles about eye-tracking and the pitfalls you need to be aware of:
Eyetracking: Is It Worth It?
The price of eye tracking
Eye Tracking and Web Usability: A Good Fit?
What is Eye-Tracking Good For?