Kevin,
Those particular slides run about $30USD per pair. For Blumotion slides the price goes to around $65-$70USD per pair. One cabinet had 30" slides and the other had 28" slides.
A rough estimate is around $500USD for a 90 degree cabinet with equal left and right faces with side mounted slides with 3 drawers. It goes up if angles are other then 90 degrees and the faces are unequal in length or they want more then 3 drawers. If the customers wants concealed Blumotion slides the price goes up to cover the additional cost. Blumotion is actually easier to install and more forgiving if the drawer is off a 1/16" here or there. The side mounts are not forgiving in this respect.