Biggest gain has been a sense of belonging. I don't personally fit into the American culture and find the directness and logical nature of Germans to be more my fit. I've also found a relationship and finally feel as though I can start a life here, whereas I felt perpetually lost anywhere I lived in the US.
Biggest loss has been the distance from family, especially during the pandemic (though of course I couldn't predict that). You don't realize how far away you are from someone until you hang up the phone with them and feel the distance set in.
I moved from Houston, Texas to Dresden. You need a thick skin in the beginning, lot of culture shocks, and hard to find work as it's very buerocratic here. Only written recommendation letters and phd's, I never needed anywhere else.
German quality of life is quite good compared to the US and the UK is a shit show due to brexit these days.
Moving to Germany from a European country is as simple as crossing the border. Moving to the US for most people in the world is a nightmare.
I for one would never go back to the US now that I live in Germany. The few British people I know moved to Germany before brexit kicks in to literally escape from the UK.
Money isn't everything, not many people change their entire life and move to other countries for money alone