On premises vs IaaS costs pretty equal

In my experience with co-location and cloud the costs over 60 months all things considered are about equal. The only real advantage I see in IaaS costs is they aren’t fixed therefore you have the option to scale down.

I found the SaaS costs over a 60 month period to be disproportionately higher though. It seems Microsoft assumes everybody is going to upgrade to new versions every two to three years.

What is everyone else’s experience with this?