db.x2gd.4xlarge is an Amazon Neptune size with 16 vCPUs, 256 GiB memory (AWS Graviton2). In US East (N. Virginia) it costs $5.909 per hour on demand ($4,313.57 per month) for I/O-Optimized storage. It is sold in 3 regions.
Prices by region
USD per hour, I/O-Optimized storage. Reserved prices are no upfront, standard. Cheapest on-demand first.