how do i see purchase history of family members
I am the administrator for my 8 year old son's iTunes. I can only see the purchase history of my own account, where can I find the purchase history for my son?
You need to log into his account to see his purchase history - on a computer's iTunes log out of your account (Account > Sign Out menu option on the current version of iTunes), and then login to his account (it should change to an Account > Sign In option). That should show you the items purchase prices.
Viewing an account's purchase history : See your purchase history in the iTunes Store - Apple Support
Or with family sharing you should be able to see some/all of his purchases (depending upon whether they are still in the store and if they've been hidden from the cloud) via the Purchased tabs in the store apps : Sharing purchased content with Family Sharing - Apple Support