These high costs are Amazon's way of telling you that you aren't architecting for the cloud. In my ~10 years doing cloud infrastrcuture on AWS I've never worked at a company had to purchase dedicated IOPS or vCPU.
You couple to AWS with your whole system architecture or you stay away.
It's a real problem if you build on a VPS as your base. I was asked to prep such a system for scale on AWS and choked on the pricing. So we settled for what they offer at reasonable pricing and if further growth is needed, will need to hit eject on AWS and just go elsewhere.
I recommend starting elsewhere and save the migration of you just use EC2.
Most places will let you scale a VPS quite well and there is a logical handoff to your own hardware where you can scale to a system with 512 vCPU and TBs of ram for less than Amazon is charging for step two.