3.0 When backordering a part, how does the system determine whether to update cost or not?

If the part that is backordered on the sales order is associated with a parts group that is updated from a price file and that part is found on the price file, the "Don't Update Cost" will be checked by default when you backorder the part.   If it is not linked to a parts group with a price file, the system will default to update the cost and the box will be unchecked.  The security permission determines whether they can change the default (found under security > parts > disallow cost change for backorders).