style of the unit weight

Hi,

Thank you for reaching out and for your patience.

To display price like this: 4,50€ /gr
Can you give a try by adding the below snippet:
https://gist.github.com/ananthatstar/21f22d1baef5b5df41b765aadc1a000c

You can add it via Code snippets plugin or via child theme -> functions.php file
Hope this meets your requirement.

Thanks
Team Themeparrot