This specifically came up because I know there were several waves of German immigrants to the USA in the 19th century, including the first half of the century, and that from 1800-~1848, I would guess most of those people came from poor rural backgrounds, and that some of the German principalities had not yet left behind feudal rights and especially dues from the peasant class, so I’d assume there’s a lot of overlap there between the two. I’m wondering less about the cost of getting a fare to the US, I assume the answer there was just save money, but the legal problem of “I am legally tied to the land and owe some lord dues, but I want to leave.” Did they have to pay a fee to the lord to be free to migrate? Just up and flee a?
This question came up thinking about Germany before some of the Revolutions of 1848, but it could also apply to Italy, Eastern Europe, any of the immigrants from China who went to California, etc.
More can be said, particularly on the German states you mention, but I covered the causes and mechanisms of migration from China here. It is also worth adding that China didn't have a per se 'feudal' economy with people actually tied to the land – farmers were increasingly forced to rent land rather than having enough freehold to subsist on, but legally speaking there was no outright serfdom – see this answer on the 'Yongzheng Emancipations'.