He is certainly willing to divulge the details. He's posted his expenses yearly. Here are 2015's: https://docs.google.com/spreadsheets/d/15RdDg3XyOGzW1T0Wjw9M...
Also in my costs are email (transactional via Mailgun, marketing via MailJet), DMARCian, AWS S3 for avatars and attachments, SSL (still paying for a wildcard, perhaps let's encrypt next time round), Google Apps for email to run the business.
It's realistic to spend around USD 10k per year running a moderately successful medium sized web business.
Found this list: http://www.s3-client.com/s3-storage-providers.html
S3 is all about controlling transfer costs, so I placed an Nginx file cache in front of my attachments and avatars and it obliterated my transfer costs.