They could always make the amount over that is given due to their cutoff enforcement being less than perfect free, as it likely already is on the free plan. That would avoid the risk of unbounded bills associated with going on a paid plan.
Most of the cloud providers have a less-than-perfect cutoff. It's worse than the cutoff of the free plan, though, because the free plan can be slowed down to have better enforcement, while the commercial plans have performance SLAs to hit.
