Original link: 37signals claims it saved almost $2m last year from cloud repatriation / Data Center Dynamics.
37signals/basecamp/DHH say that they are saving 1.9 M$ per year by leaving AWS/GCP and self host. And they expect even more savings when their multi-year contract with AWS for S3 run out.
It seems very likely. They probably have a relative stable load with no crazy scale up or scale down need. I believe they self host is their hardware in a hosting center not in own data acenter (which tend to be very expensive). They likely have in-house expertise in the few services they need, so they don't save perople from using AWS managed services.