It's not about whether it's worth it. I have no idea if $73/mo/cluster is more or less than what GKE is worth, but you can't ignore the time-varying aspect of this change. If GCP had started at $100/mo and just announced a price drop to $73/mo, your customers would probably be cheering, even though you'd be charging them the same! They'd be happy about being loyal to you, thankful that your offering gets better over time without asking, etc.
Let me put it another way. Lunch perks at Google are probably worth way more than $73/mo. Googlers would probably not feel too great about having to start paying that amount... Even though it's also worth it, people working hard to prepare food, etc.
It happens time and time again that GCP paints itself in a corner with an unsustainable offering and finds itself in a situation where it has to dent customer trust by hiking prices or retiring products on short notice.
Why?
GCP is in no position to pull this off, competitively. Now doesn't seem like the time to pull unit margins up. Google could do so on ads or with Maps API because it has the best product by far in those areas. But not in Cloud, a market where stability is a feature, and GCP is a late, small player against larger competitors who are giving customers a much more stable product.
It doesn't matter if GKE is the best thing since sliced bread, and keeps getting better — as the CTO of a cloud-based business, you have to decide whether you want to build on it over the long run and take the risk of it becoming super expensive over time; there's not a lot of reassurance that this is even a concern at Google at this point.