Comment 17 for bug 779145

"stock.moves are created way before they are processed (and the cost price can change)"
Yes, but cost price is not an element of stock, is an element of accounting (cost) and stock.moves generate accounting moves when is processed (at stock.move.action_done as you know). In V5 and also in V6 we had to put price_unit in all stock moves for a good hystorical preview of stock moves values. Otherwise, sum of the values from accounting will be different from stock move values if standard price from product is changed in time. Catching errors generated by transfers values from stock moves to accounting is a nightmare without price_unit in stock.moves.
Thanks