I 100% agree it's all trade-offs. I think cost is important, but in that scenario it's going to cost them a lot more in time to split out and maintain several services. Devops was only one example. Their development speed will also likely slow down by a good margin as they now have to worry about inter-service communication and all that comes with it (keeping schemas aligned, making sure the services can actually talk to one another, etc.).

I think services are a useful tool but for most problems you can get incredibly far with a monolith. I think a solid approach is to identify where there's a bottleneck in your monolith and extract that instead of splitting the application up for the sake of having separate services.