How can I modify cart page prices for volume discounts?

Shopify Apps

Topic summary

Goal: implement tiered volume discounts that display correctly in the cart.

  • Setup: Product metafields define price and quantity tiers (e.g., 8.00 at 10 units, 7.50 at 20, 7.00 at 1000). A custom product page table lets customers enter variant quantities and shows a discounted total.
  • Issue: The cart page still displays standard prices; the calculated discounted total from the product page is not reflected in the cart.
  • Constraints: cart/update.json appears to allow only quantity changes, not price modifications. All work so far is via Liquid templates.
  • Ask: Whether achieving cart-level price changes requires building an app/extension, and if so, which API to use. Seeking a simpler approach but prefers building a custom solution over installing an existing app.
  • Media: Screenshots illustrate metafields, the product page quantity table, and the cart showing original pricing.
  • Status: No confirmed solution provided; a follow-up post asks if a resolution was found, indicating the thread remains open.
Summarized with AI on January 12. AI used: gpt-5.
1

I am trying to implement a volume discount system.
On the admin product page I have added 6 metafields for pricing tiers and quantity tiers:

On the shopfront product page I have replaced the regular add single variation item to cart with a table that displays all the variations where the customer can enter quantities for each one. Below this I show the total that includes the pricing tiers discounted from it:

product.jpg
product.jpg1396Ă—1048 76 KB

Now I come to my problem. How do I send this amount to the cart? As it stands, when the customer goes to the cart page, the original amount is shown along with the standard pricing:

cart.jpg
cart.jpg1396Ă—1048 56.7 KB

After reading some docs, it’s apparent that we can not update these fields using the cart/update.json, just things like quantities etc.

So far everything has been done by editing the template liquid files. Am I to assume I can only accomplish this by building an app or extension? And if so, which api should I be using?

I’m aware there are already apps in the Shopify app marketplace that can do this but I want to create my own. Or even better, is there a simpler way?

Any help would be greatly appreciated. Thanks.

1 Like
2

Hey @Nortski ! hope you are doing good.
have you got any solution ?