Forgive me for a dumb question from someone who doesn't do cloud computing currently : the units are really $/GB/time period, yes? What is the time period? One hour? day? month?
AWS bills instances hourly; both Azure and Google Cloud bill by the minute (albeit with a minimum of 10 minutes). For data analytics that you want fast turn around time for, this ends up being a big deal: a 30 minute job is literally 2x less expensive than "round up to an hour". This also shows up in auto scaling of services, since a standard business day of traffic obviously only has a fairly short actual peak combined with what is ultimately fairly short term load.
Disclosure: I work on Google Cloud.