> I find it hard to believe that with a list of major enterprise clients, they can't afford several thousand dollars a month?
They can probably afford it, but if every piece of your stack needs that kind of money you run out of money fairly quickly.
> Developer costs in USA run about ~$5-10k/month
They are based in the UK.
> Would be curious to hear about the number of dev-weeks they have spent learning all the stuff they mentioned, building it, troubleshooting any issues, and keeping the system running and up-to-date.
It's just an SMTP server, not rocket science.