Vanilla behavior of updating the Cost(COST_PRI) by a Dynamic pricing procedure workflow

Dear All,

One of my customer have observed in production that there are some null values been found against Cost field for specific Service Order Type records. Again this issue is not happening currently in any of the environments.But to know what it was caused this issue further, he would like to know following:  

What is the vanilla behavior of updating the Cost(COST_PRI) by a Dynamic pricing procedure workflow. Can someone through light on this ?

As seen this is happening through S_ORDER_ITM_PRI table.  All that we may need now is to find how the costs would be loaded on to this table S_ORDER_ITM_PRI as cost field on order gets populated on to UI using this joined field.