Sure - you were hosting your DB just fine with 100 customers using standard SSD, but now at 1000 you're blowing your IOPS budget and need to upgrade to premium SSD. The premium SSD costs twice what the standard SSD does for the same space - your usage will not have doubled.

Or - god help you, you were hosting your db just fine with 100 customers using a small VM, and to avoid having to think about it, you've decided to move from a self-managed db on a VM to something like Cosmos DB. No growth in usage at all from you, but your costs are about to shoot way up.

Or - I've added a customer in a region that has poor connectivity to my current region of choice - oops, setting up edge services closer to them is going to hurt. Now I'm sending data between regions, incurring all sorts of costs between services that I wasn't with a single region setup.

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My experience with the cloud (and I've been a heavy user of both Azure and AWS, not as much GCP) is this: There are bands of costs, within that band, costs will tend to grow linearly as you grow.

The problem, is that you will outgrow the band you're in. There is a hard limit on something that you weren't thinking about (IOPS, for example) and once you hit that you have to jump to a different band with a new cost structure.

Usually, that means increasing base spend by a large amount compared to usage, and then getting slightly better cost/use at the new higher base.