@mju - Ah OK. Yes, sometimes companies charge A LOT because you have a business and they think you have more money than an average customer. The place I have used in the past (Clevver) charges a lot too for ‘Registered Address’ service which is 89,95EUR a month, but their ‘Business Address’ service is only 19,95EUR a month (plus 5,95EUR a month for their basic mail service). If you are looking to incorporate in Germany, you might be stuck paying the higher price, for freelance/sole proprietorship (e.g. so you can put their address on your business card, receive official mail, etc) maybe you can get away with paying the cheaper price.
You can check their website and see: https://www.clevver.io/locations/?filter=inc,la - others here may have other tips - but if it doesn’t need to be Germany, you can look at other (cheaper) countries too.
Best of luck!
Jim