Is the rising court costs legal?

My husband has had a garnishment on his wages for several years and can finally see the end in sight. He receives documentation from his employer of the debt collector's frequent but random renewal of this garnishment every few months or when they renew, I can't tell. So I started going through the paperwork to see exactly where we are at on getting this finalized. As I look through and compare the paperwork, you can clearly see where the "court costs" rise a lot every time they renew this: March 2010 $625.80 - Sept 2010 $728.80 - Feb 2011 $831.80 - Aug 2011 $998.80 - Jan 2012 $1106.50 - Dec 2012 $1327.90 - Nov 2013 $1549.30. Is this normal and if so why?