How do print shops set quantity break pricing?

Split each product into fixed cost per order (file prep, proofing, setup, packing) and variable cost per piece (materials, ink, per-piece labor). Set rungs so every unit price clears the variable cost, recover the fixed cost with a setup fee or minimum, and start discounts around 25 pieces with bigger steps at 50 and 100. Check each break: with all-units pricing, a deep discount can make a slightly smaller order cost more in total.