I've just shifted my SWE infrastructure from AWS to Hetzner (literally in the last month). My current analysis looks like it will be about 15-20% of the cost - £240 vs 40-50 euros.
Expect a significant exit expense, though, especially if you are shifting large volumes of S3 data. That's been our biggest expense. I've moved this to Wasabi at about 8 euros a month (vs about $70-80 a month on S3), but I've paid transit fees of about $180 - and it was more expensive because I used DataSync.
Retrospectively, I should have just DIYed the transfer, but maybe others can benefit from my error...
FYI, AWS offers free Egress when leaving them (because they were forced to be EU regulation, but they chose to offer it globally):
https://aws.amazon.com/blogs/aws/free-data-transfer-out-to-i...
But. Don't leave it until the last minute to talk to them about this. They don't make it easy, and require some warning (think months, IIRC)