You mean people aren't just cutting most of these costs out by using Amazon hosting services?
Amazon is pretty high-end and not economical for a small masternode owner, unless they are using Amazon's free tier.
So the fact that many masternodes are observed on Amazon says one of two things: 1. Small masternode owners are using the free tier, meaning there aren't hosting costs; or 2. Many masternodes are owned by large masternode owners who can justify Amazon's higher hosting costs. Maybe some of both, but I suspect mostly 2, since the free tier runs out. Scamming is possible, though.