This carries benefit for both the business and consumer; For the business: Google carries zero risk of post-pay billing as you are paid upfront + they are earn

This carries benefit for both the business and consumer; For the business: Google carries zero risk of post-pay billing as you are paid upfront + they are earning interest on the aggregated cash they will either refund or pay to the telco(s) at the end of a month. For the consumer: You are effective pay as you go, so you don't pay for unused data plus you have an upper limit on spend. The interest loss for money in holding is minimal at the individual level. And given this is likely recurring billing (so I doubt for most people they will ever get actually paid back) you simply keep a float in your google account and top up the difference each month.