Using Collections or Group Product Types in Example Tiered Pricing Script

Shopify Partner
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I had looked around and couldn't find anyone else asking this, but the "Tiered pricing for bulk purchases" example Ruby script on the page found at does almost exactly what I need it to do.

However, the discounts work on a per product basis, I'm trying to get a way to have it count towards either all products in a collection or just all the given product types combined, instead of a per product type basis. I have been digging around in the script, but I'm not very seasoned when it comes to Ruby itself. 

If anyone has some insight or something that could point me in the right driection on this, it would be greatly appreciated!