A lot. They wouldn’t spend $70 for 1 item. They will buy a few packs here and there and that’s $100 spent and they didn’t even know.
My kids did that. I gave them a debit card with some allowance and next thing I know, $50 was spent on a micro transaction. $5, $7 and then a few more clicks, $50.
Google policy is they only refund the last transaction 1 time for an app.