I followed Andrea's solution (thanks!) in https://www.odoo.com/es_ES/forum/ayuda-1/can-i-configure-multiple-vendor-barcodes-and-associate-them-with-one-specific-product-202615 for multiple vendors and barcodes per product.

Problem is, on a purchase order, if we are buying a box of 500 units of product A from vendor X, we need to calculate the unitary price rather than the price of 500 units. Say the box is $753, then we need to divide 753/500 = 1.506 and input that as unit price. If you have found a workaround or a way to solve this, I'm sure the purchasing dept. guys will be more than grateful with you.

We believe it might be related with Units of measure vs Product Packaging, please let me know what you believe the best solution is.

Best,