I'm setting up a wine store, starting simple with one SKU of red, one SKU of white, one SKU of rosé, and developing to have multiple SKUs of each wine. From each of the product pages, I want my customers to be able to buy either 1 bottle, a case of 3 bottles or a case of 6 bottles (all of the same type SKU from the same product page, not mixed cases). I don't want to set these up as a variants as the base product SKU will remain the same. Setting up as variants also requires you to input the quantities of 1/3/6 bottle cases available, when in the warehouse there will be lump quantities of single bottles available and they will be packed into cases of 1/3/6 depending on the quantity selected by the customer (ie not prepacked because that offers no flexibility if one case size is more popular). There will also be different pricing for 1/3/6 bottles to offer a discount for larger quantities. (Eg 1 bottle costs £10, a case of 3 costs £25 and a case of 6 costs £40). On an inventory side this will make it easier to manage how many bottles we have available in total rather than break it down into prepacked cases.
How can I make it so the customer can set the quantity of the same product they want (specifically 1/3/6 with no other quantities available), with the price changing to reflect this? Empathy Wines does this well on the front end of their site; https://empathywines.com/products/red with the 3/6/12 bottle offer, although without the discount for larger quantities.