We still run and manage our servers and save a metric ton of money wrt. "cloud" offerings.
When "cloud" or "serverless" will be cheaper than managing your own dedicated servers, then it will actually be useful. Until then, it's just marketing.
In my experience a dedicated server will be cheaper most of the time.
I'm using Hetzner for most of my customers (small & medium-size companies) and for several services offered by Amazon a dedicated solution is just cheaper. I always calculate the prices beforehand for several scenarios and self hosting scenarios are almost invariably cheaper (storage, computing etc.).
This does NOT mean it's better. Hetzner's servers are in Europe, they're not infallible (but usually they replace the hardware within 30 minutes or so), you need more time for the initial setup than with AWS, and obviously you can't scale them up in the same way. However, they're cheaper.
Marginally cheaper? In the statistical sense - each one is physically cheaper. But if you count managing them yourself, backing them up, fixing them when they break? Count the room they take in your house/office? If you have enough, count the salary of the person hired to install/manage them as you expand?
My experience is that you need a competent person in each case - whether the data is stored in S3 or on a dedicated server, whether you use EC2 instances or doing the job on your own server.
For something like 40€/month you get Core i7, 32 GB RAM, 2x4TB HDDs, 1 GBps port and 30 TB included. In this 40€ the cost of storing the server, cooling it, power, etc. is included:
https://www.hetzner.com/dedicated-rootserver/ex41
When things break, they repair it.
In my case, they usually break once a year - sometimes the PSU, sometimes a hard drive (no a problem with RAID 1 already in place). It all depends on your needs.
Both "cloud" and "serverless" are cheaper if capacity needs are opaque (high growth or unpredictable swings.) If you have predictable capacity needs, I agree that dedicated servers are a better value.
It already is for some of the things I'm doing. I have a lot of data in s3 and process it with lambda, meaning I can run a bunch of things I want very quickly by starting 100+ concurrent processes with virtually no management time from me, and it's cheap.
When "cloud" or "serverless" will be cheaper than managing your own dedicated servers, then it will actually be useful. Until then, it's just marketing.