Help Guide › Owner
Each purchase of a product keeps its own vendor, lot number, unit count and landed cost. Buy Retatrutide five times from four vendors and you keep five cost records, not one.
The product's cost basis is the weighted average of what you actually paid — 10 units at $23 and 50 at $18 gives $18.83, not $20.50. That's what your inventory value uses, so restocking at a better price shows up honestly instead of being overwritten.
A sale's own cost is finer than that. When a sale records which batch it came from, its profit uses what that batch cost, not the average — so selling from the $23 batch and the $18 batch no longer look identical. The average is the fallback for a sale that doesn't name a batch.