This pitfall of "serverless" has been widely known since people started abusing lambda to be "always on". Serverless is a PaaS gaslight to make you pay more for the perceived convenience.
Serverless is often cheaper just so long as your workflows are bursty/infrequent. For example, we don't need to pay to permanently rent/colocate a beefy server, just to run a batch job once a week.
If you have a constant base load of requests, lambda is just the wrong tool for the job.
Even if it's pretty bursty, usually a perm server is still cheaper. Running the server only half the time isn't burning too much money since AWS is already 10x the cost of raw compute. You need really bursty workloads to make serverless make sense.
If we're talking about relatively small workloads, and relatively stable traffic, then sure.
But I think for large workloads with unpredictable requirements, the capacity planning alone in a perm setup is a nightmare for most early-stage businesses. Spinning up an extra hundred instances in EC2 takes minutes - getting the same number of boxes installed a colocation facility takes weeks at best
It's not a gaslight, but it's only cost effective for specific usage patterns. It's only a "gaslight" if you think you need to run every workload the same way and don't cost estimate before you roll it out.
If you have a constant base load of requests, lambda is just the wrong tool for the job.