Here is a list of all prices from possible upgrades:

FileSharing (one year) = 9,90 Euro
FileSharing (perpetual) = 19,90 Euro

Home old (perpetual) = 29 Euro
Home new (one year) = 19,90 Euro
Home new (perpetual) = 39,90 Euro

Business old (perpetual) = 79 Euro
Pro new (one year) = 39,90 Euro
Pro new (perpetual) = 79,90 Euro

FileSharing (one year) -> Home (one year) = 10 Euro
FileSharing (perpetual) -> Home (perpetual) = 20 Euro
FileSharing (one year) -> Pro (one year) = 30 Euro
FileSharing (perpetual) -> Pro (perpetual) = 60 Euro

Home old (perpetual) -> Home new (one year) = for free
Home old (perpetual) -> Home new (perpetual) = 11,97 Euro (30 % from 39,90 Euro)
Home old (perpetual) -> Pro new (one year) = 20 Euro
Home old (perpetual) -> Pro new (perpetual) = 51,97 Euro (11,97 Euro + 40 Euro)

Home new (one year) -> Pro new (one year) = 20 Euro
Home new (perpetual) -> Pro new (perpetual) = 40 Euro

Business old (perpetual) -> Pro new (one year) = for free
Business old (perpetual) -> Pro new (perpetual) = 23,97 Euro (30 % from 79,90 Euro)

(You need one license for each computer! All prices including German Vat.)