10% of 1B is 100M.
100M tickets in how much time? Let's say a year. And it takes on average 5 minutes to respond to 1. That is 500M minutes. So you need a team of ~1500 people to respond to 100M tickets in a year. Not that bad eh.
Separately, your time estimates are much too low.
True that 5 mins per ticket is too less. But I don't think any paid tech service has 1B customers. (users yes, customers, I don't think so).
10% of 1B is 100M.
100M tickets in how much time? Let's say a year. And it takes on average 5 minutes to respond to 1. That is 500M minutes. So you need a team of ~1500 people to respond to 100M tickets in a year. Not that bad eh.