We have a policy that our customers are responsible for all their business-related input, but we make the decisions about the technical implementation. Every technical decision that the customer wants to make basically costs extra.
In this case we built a rather simple multi-tenancy B2B app using Laravel, with one database per tenant. They planned to start with a single customer/tenant, scaling up to maybe a few dozen within the next years, with less than a hundred concurrent users over the first five years. There were some processes with a little load, but they were few, running less that a minute each and already built up to run asynchronous.
We planned a single Hetzner instance and to scale up as soon as we would see it reaching its limits. So less than 100 €/month.
The customer told us that they have a cooperation with their local hosting provider (with "special conditions!") and that they wanted to use them instead.
My colleague did all the setup, because he is more experienced in that, but instead of our usual five-minute-setup in Forge (one of the advantages of the Laravel ecosystem), it took several weeks with the hosting provider, where my colleague had to invest almost full time just for the deployment. The hosting provider "consulted" out customer to invest in a more complex setup with a load balancer in front, to be able to scale right away. They also took very long for each step, like providing IP addresses or to handle the SSL certificates.
We are very proud of our very fast development process and having to work with that hosting provider cost us about one third of our first development phase for the initial product.
It's been around two years since then. While the software still works as intended, the customer could not grow as expected. They are still running with only one single tenant (basically themselves) and the system barely had to handle more than two concurrent users. The customer recently accidentally mentioned that they pay almost 1000€/month for the hosting alone. But it scales!