Less than 5% of commercial storage capacity was SSD of any flavor in 2015 (NVMe probably less than 1%), and the price-per-GB was anywhere from 5-15x. NVMe hardware RAID didn't happen until 2017, and AWS SSD via EBS was capped at 320 MB/s (~500 MB/s with striped EBS volumes). Before 2015 it was capped at 160 MB/s.

In practice even NVMe SSDs at the time were maybe 10x faster for sequential R/W and maybe only 200-500x for random I/O. Most databases in 2015 were limited by serial dependency chains like walking a B-tree to figure out what nodes to read next and couldn't max out what an NVMe was capable of. Not to mention we were stuck with libaio in 2015 that made O_DIRECT ops synchronous.

So the OPs claim of reading multiple terabytes of data in seconds on AWS in 2015 literally wasn't technically possible.

SSDs simply were not as ubiquitous in 2015 as they are today, and I didn't know anyone using them outside of mission critical systems were the cost made sense.