6.12 Good to know — products

Retire, don't delete. Deactivating a product removes it from pickers while its history, balances and documents remain intact and reportable. Deletion is for mistakes caught before use — a product with a past is a product the record needs.
The SKU is the product's passport. Unique in your company, printed on documents, searched everywhere. Choose SKUs your warehouse can say out loud; the system will honour them exactly as typed, forever.
A price is never zero, and "free" is not a price. Promotions and giveaways are handled on the document — a discount, a zero-value line where the workflow allows — not by teaching the grid a zero it will then faithfully apply to everyone.
Prices and costs are separate permissions, on separate pages. If a colleague "cannot see what things cost", that is the design working (§6.8) — not a missing screen. And if someone needs both, that is a decision about trust, made in roles (Chapter 16), not a setting in this chapter.