McCarney's assistants were only paid thru the length of their contract, which was 1-year (thru May or June, 2007). The total cost of the 2006 McCarney-to-Chizik change was $675,000:
http://www.usatoday.com/sports/college/football/big12/2006-11-08-mccarney-resignation_x.htm
The cost of the 2008 Chizik-to-Rhodes change is $1.75 million per the Waterloo Courier. Less the $750k Auburn buyout, ISU's cost is $1 million.
The cost of the Morgan-to-McDermott change was $1.525 million ($750,000/year x 2 years for Morgan's buyout, plus a $25k payment to UNI for hiring McDermott).
Don't forget that in his first 18 months, Pollard also replaced the wrestling, gymnastics, soccer, cross-country, track-and-field, women's golf, tennis, and softball coaches. Those are not high profile positions and the cost was not publicized, but it wasn't free.
All of this started a year after paying Larry Eustachy $960,000 to go away.
If we add it all up, ISU has spent about $5 million to fire and replace coaches from 2003-2008. You are right, it's a huge number. Embarassing, even. If that money was an investment that made our teams better, it might be worth it. But the only thing we have to show for all that money is teams that have gone from bowl games and NCAA/NIT tournaments to last place in the conference. If this were a business, the guy in charge would be fired.