With insurance, then its always what it would cost to replace.
A couple of my early machines are not replaceable, so i estimate these at how much i would want so i could go get another rare title without having to think too much about it.
If you paid $3K for a machine that you reckon is worth $5K then value it at $5K.
One thing is for sure - the insurance companies always want to down pay you, so always estimate upwards