This is a first-degree smart argument. It presents a seemingly non-obvious idea that makes sense in retrospect.
However I happen to work at the experimentation team of a hyperscaler so I have a different perspective.
First, we aren't always saturating all of the potential experiments we could be running. The reasons are different, but essentially it takes time and effort to build those experimental features. If that cost trended to 0, we could make sure to have a queue of experiments deep enough.
Also in our side we need to do development work to support new features and products. We have a backlog long enough to keep us perpetually busy. If dev cost trended to 0, we could always be ready to provide our customers what they need.
Speaking of new products, each one our company comes up with comes with extra effort to support in our side, and yet more effort to produce dozens of AB test to validate new functionality.
This is not talking about ongoing maintenance effort. Bugfixes, upgrades etc. take a non-trivial amount of effort to keep up.
And this is only inside our little experimentation team. What about security, reliability, scalability, efficiency... it makes me wonder if OP has experience running products at scale.
Instead I'd like to think that dropping the cost of development by orders of magnitude changes the equation of how we create products.