These are personal opinions, not fully factual, I've only worked with 2 cloud based start ups (neither full time).
Cloud services are barely a convenience to the customers/business that run on them. For a start up buying 50-100k in servers starting off is shocking but in most cases high usage cloud computing for hosting/databases will add up to that quickly.
The only thing 'cloud' actually does for its customer is prevent them from actually buying computers and renting rack space. Which isn't 'that' expensive (20k or so for a base line server), and 150 a month in rack rent.
Cloud lowers the bar of entry, but once you've entered staying with cloud isn't optimal.
Its expensive since Amazon uses DNS based CDNs. Each pop requires them to assign you a dedicated IP. They don't do shared certs like other CDN providers. One nice thing is that you can use an EV Cert.
