Harmony is using t3.small instances (2 cores, 2GB RAM, roughly $15.23 per month) along with 64GB of storage (standard EBS storage, roughly $6.4 per month) and 100MB bandwidth.
We're finding recently that actually our greatest cost is becoming the network data since we are sending so much data around the network. I need to make a more accurate measurement of that cost, but the current estimate from our bill is ~$45 per node per month.
AWS M5A Large ~ $100 per month (highest performance)
AWS t3.small ~$22 per month (minimal requirement)
Vultr High Frequency 128 gb ~$24 per month (high performance)
Vultr Cloud Compute 80 gb ~$20 per month (good performance)
2 vCPU (core), 2G RAM, 60 GB per half year, 100M+ networking bandwidth
Harmony is reviewing best practices to reduce both data storage and transfer costs.