Instead of hunting through theme files and modifying Liquid code, you might want to consider using an app as a simpler alternative.
Our app Weario handles exactly this scenario without needing to modify theme files. While it’s primarily designed for fashion brands showing “per wear” pricing, the labels are fully customizable so you can display a “per unit” price for your wholesale packs.
For your complex pack configurations:
Set up Product Sets for each pack type (S-M-L-XL(2-2-2-2) = 8 units, etc.)
Configure the label to show “per unit”
App embed blocks work on collection pages
Displays the calculated unit price below your pack price automatically
The advantage is you avoid the complexity of:
Finding the right theme files in Symmetry
Duplicating your complex Liquid logic across multiple files
Maintaining custom code when themes update
Debugging collection page vs product page differences
Since you already have the unit calculations working on product pages, this would give you the same functionality on collection pages with much less technical complexity.