As others have already noted (and I should stop reading this and go to bed, it's after midnight here and I have to work in the morning!) we have plenty of competition, and it's either plastered with ads or similarly priced, because that's what it costs to run a service while giving your staff a decent living and continuing to improve your service over time.

As I said here: https://blog.fastmail.com/2016/12/01/fastmail-advent-2016/

... one of the most common questions was "aren't you worried about giving away all your secrets?" Actually, we really are not. Running an email service is hard work, and providing the speed, reliability and stream of new features would not be easy to replicate. So we're happy to share our stories...

We contribute a lot to open source, and we're doing a lot in the standards space now to make sure email remains open. Topicbox is built on top of a draft of the JMAP protocol which is currently being worked on at the IETF, and will be updated to follow the standard. We have staff going to CalConnect to work on calendaring standards in a couple of weeks because we're investing in advancing the field as well. That also costs money, and we're self funded, so we can't afford to sell email accounts at a loss.

It also means we have no secret customer. Our paying customers are our actual customers, not the product we're using to pump up the valuation or collect data from. It's a simple business proposition, money for service. I'm proud to charge money for what we do.