I think their key advantage is sales. Imagine a product that adds a small amount of value to a company but requires a long drawn out sales process including research on available vendors, pricing, security, use cases, determining requirements, etc vs a developer going to the AWS console and clicking "create databrew". It's no competition.

And with sales taking up such a huge percentage of a lot of these SAAS companies revenue, Amazon can pass the lack of sales to the customer as cost savings. Skip the sales process and the sales cost. win win.