Europe invites Apple, Google to discuss 'in-app' purchases
reuters.com
reuters.com
Set the app store to require a password for any purchase.
My kids or I have never racked up any huge bill.
See for example the factoid that 0.15% of players spend over 50% of the money in f2p games (and these games make tons of money):
http://www.gamesindustry.biz/articles/2014-02-26-15-percent-...