We sell out software to the big banks and we don't have a single salesperson in our team. Everyone call us. The reason for this is that we have been in national newspapers with awesome articles, which is great marketing.
I'm sure we could do even better on the international market with a sales team.
But AWS also often start as a $10/month product, and then one more, and one more. I think that's a huge portion of their success - it's easy to ramp up the cost slow enough and in small enough steps to not trigger any major approvals until it's "too late". People usually move off AWS first when if it gets to be enough of a cost pain-point to make higher ups take notice.
Isn't that the point of cloud computing? So you don't have to worry about datacenter capacity until it becomes a major cost center?
Here's how that works in concept, for example:
Microsoft didn't hand-sell every individual copy of Windows 95 at every individual retail location. They did sell, big time, at the macro level however, which made the micro sales possible. That's how AWS works, Amazon captures the macro, the micro takes care of itself for the most part. If you're AWS and you capture dozens of impressive start-ups and enterprise players, the headlines and blog posts that are written as a consequence will micro sell as a consequence to countless smaller businesses for you. Not to mention, Amazon simultaneously pushes AWS at small businesses in numerous subtle ways, including on their site (which of course happens to be a giant advertising platform that reaches every business owner in the US).
You can sign up and AWS without any customization. Even if you spend $10k/month on AWS, you don't really need to talk to AWS to create a custom deployment (from what little I know of AWS - might be wrong).
But if you're talking about a solution that requires customization, or if you want volume discounts, you will want to speak to a salesperson.