The main difference is that if you built your product on their platform, you don’t have the option to pick a different vendor for what you’ve already built like you would for subscriptions or eggs. It feels much more akin to extortion to me.
You built your product on their platform and agreed to the terms they set. Thats a level of commitment you put in. Them changing it afterwards is forcing you to agree to new terms that you wouldn’t agree to if you weren’t forced.
If the issue is using their servers, or keeping the runtime code updates, there should at least be the option of self hosting or locking into an older version.
Having said all that, I know very little about vendor contracts and don’t doubt you when you say legally its the same as any other price change. It feels different because of the lack of choice.