Possible theory why they did it: To my understanding, you don't pay for traffic, you pay for network capacity. Maybe US instances aren't getting the uptake they had hoped for, and they are looking lower some costs by reducing their network capacity (they are a very German company and care a lot about efficiency).
Hetzner is very cheap and still profitable because classic "economy of scale" and vertical integration. They own, build, and operate all their data centers. This comment goes into more details[1], but it's possible this doesn't really work out in a foreign location like US.
Counterpoint: They could've lowered their capacity without changing plans if they were indeed seeing lower uptake, and increase capacity as/when it's needed if it did indeed ever pick up. They wouldn't be the first provider to put products out of stock whilst they scale back up.
That doesn't explain a 20x regional pricing difference for the same service (outgoing bandwidth). It's either a malicious change to extract exorbitant rent from customers (hostages at that point) or buying enough bandwidth is whole lot more expensive than they calculated and it reflects costs to provide the product (a virtual machine a specific traffic cap).
If its mostly the later case they really fucked up their customer communication. They should care enough to provide their customers with time to respond and transparency to (re-)earn the trust a hosting provider requires.
If it were malicious, they would have increased prices in Europe as well. They could try and extract money from European customers just as much as American ones.
And the bandwidth pricing is still quite cheap, $0.001/GB. Major cloud providers usually charge nearly 100x that (AWS 90x, GCP at 85x or 120x depending on whether you want standard or premium, Azure at 80x or 87x depending on standard or premium).
You used to get 20TB for free and now you get 1-8TB free. If you had to pay for 19TB, that's another $19. If you had to pay for 19TB from a major cloud provider, that'd be $1,556-2,335. Even if you had DigitalOcean, they'd be charging you $0.01/GB (10x) and you'd be hit with a $190 bill.
I think the issue is that in the US, they don't have their own network. They peer with a single company in Virginia for 200Gbps and then pay for transit on 1Tbps. That's a lot of transit to be paying for - and 5x more transit than peering. In Europe, it looks like they have their own network between Finland, Germany, France, Amsterdam, UK, Austria, and Czech Republic. They also have a much better ratio of peering to transit. So they can use their network to carry the traffic to a lot of Europe and then maybe they have peering arrangements to handle most of their traffic when they need to hand it off.
In Europe, they're more likely to face owner economics while in the US, they're effectively renters - and the more their customers use, the more it's going to cost them.
If this were really a cash grab, it's a pretty terrible cash grab. It will certainly impact some users, but the maximum it will impact any user is $19/mo (if they're on a server with only 1TB of included traffic). But most people don't use many TB of traffic. Consuming all Bluesky posts in zstd compressed JSON is 30GB/mo. These weren't servers that had unlimited traffic on a 1Gbps port. They had a 20TB limit. If you were hitting that and intend to continue hitting that, it's another $12-19/mo.
If I had to guess, I'd say that they probably thought they'd expand more in the US and build out a fiber network here (as OVH has done), but that didn't happen and now they're looking at continuing to pay transit for the foreseeable future. Though I feel like the optics of this are pretty bad given that most people probably use less than 1TB and those users will still feel like something is being taken from them (even if they were never using that much anyway).
American traffic is expensive and they scarcely do peering agreements. And the backbone providers are probably jacking up the prices to boost revenue in these inflationary times. Eu users are not affected because the Eu invested heavily in the internet backbone and everybody peers with everybody there. In the US the isps cripple any effort to improve the internet infrastructure for profit.
Hetzner is very cheap and still profitable because classic "economy of scale" and vertical integration. They own, build, and operate all their data centers. This comment goes into more details[1], but it's possible this doesn't really work out in a foreign location like US.
[1]: https://forumweb.hosting/13663-why-are-hetzners-dedicated-ho...