It depends on the project and how are you managing it.

In this case, every 5 students they were managing a single instance, with Java backend and a React frontend, with robust testing (and they didn't build the solution from scratch, rather the "inherited" one, and they had to evolve it). And instances were AWS (yet, we got the running instances for free, I only paid for CI/CD resources).

But I've seen big sites with millions of users running safely in cheap instances. So, you may net a lot of money, but you will pay for the servers either way. So the only price is CI/CD.

And on the other hand, I have seen companies spend ridiculous amounts of money on custom-made solutions. So, yes, it can be very expensive, or a lot cheaper than what it seems. Yet, I believe that the big difference in pricing here is the quality of the automatic tests. Better and more reliable tests, the cheaper everything becomes.