Having recently looked at eye trackers myself, a good stationary setup will run you about $40K to $50K. Regarding the Tobii, earlier models had some accuracy issues:
Morgante, J. D., Zolfaghari, R., & Johnson, S. P. (2012). A critical test of temporal and spatial accuracy of the Tobii T60XL eye tracker. Infancy, 17, 9-32.
The following paper compares eye tracking with Tobii and SMI systems under conditions of different head movements; SMI eye trackers had some data loss issues:
Hessels, R. S., Cornelissen, T. H. W., Kemner, C., & Hooge, I. T. C. (in press). Qualitative tests of remote eyetracker recovery and performance during head rotation. Behavior Research Methods.
A colleague of mine who uses eye tracking extensively in his research recommended EyeLink over Tobii due to data loss issues with the latter.
My understanding is that Tobii, SMI, and EyeLink systems all work with E-Prime.