Tim, it will depend some on where you are, but here in Texas the septic inspection (by a septic pumping company or contractor) is normally around $300 dollars and includes pumping the tanks.  I'm not sure of all of the specifics but I know they actually uncover the tops of the tanks and pump and inspect the tanks and other associated components that are not accessible during a normal home inspection.  A pumping or installation company can give you more specifics on what they look at.  There are system types other than the standard that we are all familiar with also, such as an aerobic system which which is more sophisticated having sprinkler systems, pumps and electronic controls and monitoring systems which would need to be checked also.  Aerobic systems are common here in the hill country of Texas because of the soil composition but you may not see them in Atlanta.  The link below has some info and pics regarding septic inspections.

http://www.agnr.umd.edu/users/wye/personel/Miller/goodinspection.html

 Jerry