[gknoy]

    2.5 million users : 24 support staff
    1 billion users   : 9600 support staff

If it scales linearly, that's about 10k support per billion users. I was going to say that a 10,000 person department for handling customer support sounds like it doesn't scale, but maybe I'm wrong, given that that is only about 5% of google's headcount.

[Aachen]

Also in terms of costs: if those support staff cost 100 grand a year in salary and other costs, staffing the 2.5M-user company with those 24 support crew 24/7 (3 shifts, let's pretend it's equally busy at 3AM) results in some 25 cents per month per user that need to be priced into the product. The transaction fees on a monthly billing system are likely higher than that of a skilled support team if this is a representative scale for the industry

I frankly doubt the numbers, surely it costs more than this for an average company?