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).