It can add up quickly if you use a couple of libraries and also have to license the OS and perhaps other software. Some proprietary software companies can be quite aggressive with what they consider as cores, e.g. if you have a large VMWare Cluster they consider every single CPU of that cluster for license costs, not just the ones the software runs on - because you could potentially scale the system up or down or do a live migration.
I'm not sure how that would even work with cloud providers, at the worst you would have to pay for the max number of cores you have used in a year (however, it's not even clear what a core is in that context with SMT and preemptable cores).
I'm not sure how that would even work with cloud providers, at the worst you would have to pay for the max number of cores you have used in a year (however, it's not even clear what a core is in that context with SMT and preemptable cores).