Their aggregate margin is typically around 30%-40% based on Amazon financials, but that reflects a lot of cost they have as a provider that you as a user wouldn't, e.g. cost of sales and the complexities of managing a multi-tenanted setup, as well as a number of huge customers that clearly are not paying list prices -anyone who is paying six figures or more at AWS and paying the publicly listed prices are overpaying (they can and do negotiate).

The margin on the list prices are clearly far higher.