But is it for aligning 3 wheels or 2?
The two front wheels are aligned using the rear wheel as a point of reference to set the toe evenly.
I use the True Laser Track system which uses four targets. I haven't seen the polaris system in use but it appears to use two rear targets.
Cost is negotiable, $129 is my normal charge but it can be lower depending on the number of units being done and the number of adult beverages provided after the fact.