I actually forgot the /s. And I guess I wasn't clear enough. This is less than a drop in the pool for them. An image build that takes them around 15 mins including setting up the VM for the build, takes me around the same time on a machine with a 6-core Ryzen 5 at 2.375GHz, with 8GB RAM. So because they're running it on their high end hardware and it still takes that long, they aren't allocating that many resources to the VM, meaning that it costs them basically nothing.

TLDR: If any of this was a cost that had any significance to their bottom line, it would have been restricted and/or monetised.