How to build properly the pricing for volume?

1. For Wholesaler or Distributor: A distributor/wholesaler will decrease the price of a product while re-selling in bulk quantity. Design a pricing strategy for volume discount such that it maximises channel profit (maximum profit for both manufacturer and retailer). You can ask for distributor selling price for different volume or looking for the selling price of similar products in the market.
2. For the retailer, the price should be constant as they get margin on the product. Now, there are several possible problems with selling in large volume to the retailer and it depends on the type of retailers. Some may not have proper storage space for your products thus can damage product, others can offer a discount on your product. Again, it will be difficult for you to monitor the demand for the product. This can affect the manufacturing and supply chain.
3. Talking about the relationship of volume with quality. It depends on your competitors and incentive for the customer to buy in bulk. You can map the customer's product line up using price piano framework. This will help you to place the product in a better price range. Secondly, you can plot a consumer incentive graph to understand pricing for an increase in quality or volume. FMCG companies use this logic to understand consumer psychology. Look at the price of Heinz ketchup bottle for a different size, you will see a trend in pricing.

Please note that for industrial product, these strategies would be different.