The really impressive thing about Valve is the amount of revenue they make with a relatively small head count. They have about 1/10 the number of employees as EA.

Seems about right. They don't have a complete monopoly and the industry seems to be making most of their money off micro-transactions these days instead of sales, something valve takes no cut of outside there own games. Meanwhile apple and google do have monopolies and take a cut of micro-transactions which accounts for there significantly larger revenue.

It might be. It's hard to know since Valve isn't a public company, so it's all estimations and guesses.