Big Business includes several options for selling different Quantities at different prices.
There is a optional feature (for a paving stone distributor) that lets you key in one unit (square feet) on one row and converts to other units (pallets and eaches) on split rows. This works with Qty Pricing to automatically set bulk price (pallet) on bulk rows.
There is another feature (for beverage distributor) for splitting one item (drink cases) into other items (individual drinks) automatically, so the inventory is kept up-to-date. This does not require Qty Pricing because each item (cases and eaches) has its own item card to automatically avoid fractional items (one case minus one bottle leaves 23).