Around 8 years ago I migrated a full company from heroku to AWS and cut costs by 3/4. At that time I remember all the startups around us doing the same, with similar results.
50 USD/mo was for 1 production Heroku app dyno (no db!), with no Redis or Sidekiq. On GKE we added Redis and Sidekiq, all duplicated for staging (on Spot VMs), for 58 USD/mo. (One single-zone cluster is free on GCP.)
What's your cost breakdown like?
And how are you finding it so far?