People really should be aware of this, yes. Even if your client /management absolutely insists on S3 for reputed durability etc., if bandwidth costs are high, you can often get 'free' extensive compute resources by hiring servers elsewhere to proxy and cache S3 access to cut bandwidth bills and run other things next to the largely network bound load.
In general I find the big problem with AWS is that cost is handled 'in reverse': developers often get near free reign, and cost only gets handled when someone balks at the size of the AWS bill. Often it turns out to be trivial to cut by changing instance types or renting a server somewhere to act as a cache. At that point people have often spent tens of thousands in unnecessary fees.
There's an underserved niche for people to do AWS cost optimization on a 'no-win no-fee' basis.
I used to help clients with cutting costs on AWS and if people were in doubt I'd often offer that.
And the savings were often staggering (e.g halving hosting costs was common; once we cut costs 90 percent by moving to Hetzner for a bandwidth intensive app even though long-term
storage remained on S3).
The biggest challenge in serving that niche is getting people to realise they may be throwing money out the window as surprisingly many people still assume AWS is cheap, and offering to do an initial review for free and not charge if I couldn't achieve the promised savings made it a lot easier. Someone who likes the sales side more could make a killing doing that.