If you have elasticity then make sure you understand the limits. Even Serverless has these knobs but for various reasons they default to high elasticity.
But many folks don’t need the elasticity at all. So you should factor that into your architectural decisions.
Generally, I tried to make exceptions to grant the refund. It sucks to get these bills and they can be quite scary.
Unless you have a real chance of bursty traffic I suggest going with compute that has more predictable costs.