I'm curious about one aspect though. The price comparison says storage is "included," but that hides the fact that you only have 2TB on the suggested instance type, bringing the storage cost to $180/TB/mo if you pay each year up-front for savings, $540/TB/mo when you consider that the durability solution is vanilla replication.
I know that's "double counting" or whatever, but the read/write workloads being suggested here are strange to me. If you only have 1875GB of data (achieved with 3 of those instances because of replication) and sustain 10k small-object (4KiB) QPS as per the other part of the cost comparison, you're describing a world where you read and/or write 50x your entire storage capacity every month.
I know there can be hot vs cold objects or workloads where most data is transient, but even then that still feels like a lot higher access amplification than I would expect from most workloads (or have ever observed in any job I'm allowed to write about publicly). With that in mind, the storage costs themselves actually dominate, and you're at the mercy of AWS not providing any solution even as cheap as 6x the cost of a 2-year amortized SSD (and only S3 comes close -- it's worse when you rent actual "disks," doubly so when they're high-performance).