The GP3 volume type is the most cost-effective option that meets the company's requirements. GP3 volumes offer performance independent of storage size and can provide up to 16,000 IOPS, which matches the company's peak requirement of 15,000 IOPS. In addition, GP3 volumes are typically more cost-effective than the io1 and io2 volume types. GP2 volumes, on the other hand, do not allow you to provision IOPS independent of storage capacity, which may result in higher costs if additional IOPS are needed.