Hello! 

Thank you for the respond, but I mean that these prices must be shown on the product page before selecting these amounts.

So when the customers arrives at the product page, the customers see immediately the discount for 10 or 20 pieces (for example).

So before selecting the amount

In Odoo 18, you can automatically apply and display multiple price tiers (based on quantity) for products like books by using pricelists.

Step 1: Set Pricing Rules

Add pricelist rules based on quantity for the specific product (e.g., "Book")

Book 15 qty as $500

Book 10 qty as $400

Book 5 qty as $300

Step 2: Automatically Display Price Based on Quantity on the Product Page

Once the pricelist rules are active and assigned

When a customer selects a quantity of 10, will automatically apply the $400 price from the price list.

Similarly, selecting 5 or 15 will trigger the respective pricing tier.