db.x2g.2xlarge is an AWS RDS size with 8 vCPUs, 128 GiB memory (AWS Graviton2). In US East (N. Virginia) it costs $1.304 per hour on demand ($951.92 per month) for PostgreSQL, Single-AZ; a 1-year reserved instance with no upfront costs $0.7563 per hour, 42% less. It is sold in 5 regions.
Prices by region
USD per hour, PostgreSQL, Single-AZ. Reserved prices are no upfront, standard. Cheapest on-demand first.