I wonder if there is a minimum age on the insurance, giving an 8 year old a phone is pretty much a guaranteed replacement at least once.
Also, 8 year old's don't need phones, I was 17 when I got my first one and I had to buy that myself!
The cost is irrelevant imo.
I think a phone is a valuable asset to a kid that plays out, etc... It means they can always get in contact with you if needed.