Of course you reduced 90% of the cost. Most of these costs don't come from the software, but from the people and automation maintaining it.
With that cost reduction you also removed monitoring of the platform, people oncall to fix issues that appear, upgrades, continuous improvements, etc. Who/What is going to be doing that on this new platform and how much does that cost?
Now you need to maintain k8s, postgresql, elasticsearch, redis, secret managements, OSs, storage... These are complex systems that require people understanding how they internally work, how they scale and common pitfalls.
Who is going to upgrade kubernetes when they release a new version that has breaking changes? What happens when Elasticsearch decides to splitbrain and your search stops working? When the DB goes down or you need to set up replication? What is monitoring replication lag? Or even simply things like disks being close to full? What is acting on that?
I don't mean to say Heroku is fairly priced (I honestly have no idea) but this comparison is not apples to apples. You could have your team focused on your product before. Now you need people dedicated to work on this stuff.
With that cost reduction you also removed monitoring of the platform, people oncall to fix issues that appear, upgrades, continuous improvements, etc. Who/What is going to be doing that on this new platform and how much does that cost?
Now you need to maintain k8s, postgresql, elasticsearch, redis, secret managements, OSs, storage... These are complex systems that require people understanding how they internally work, how they scale and common pitfalls.
Who is going to upgrade kubernetes when they release a new version that has breaking changes? What happens when Elasticsearch decides to splitbrain and your search stops working? When the DB goes down or you need to set up replication? What is monitoring replication lag? Or even simply things like disks being close to full? What is acting on that?
I don't mean to say Heroku is fairly priced (I honestly have no idea) but this comparison is not apples to apples. You could have your team focused on your product before. Now you need people dedicated to work on this stuff.