$400M in Surface revenues. At even a generous $400 unit price, that's only 1M sold this quarter. Probably closer to 700K if you consider some of them being Surface 2 priced up to $900.
> There are costs associated with each sale, not everything is revenue.
"Costs associated with each sale" are irrelevant when considering revenue.
If you spend $400 to make a $500 sale, it's the same as if you spend $100 to make a $500 sale. Both are $500 in revenue. What's different is income, which is revenue minus costs.