I have learned some through trial and (Lots of) errors. Basically, each time you create a materials list, and include pricing for the items contained therein, you can select these items and update the Master List with these cost.
For instance; Your Master List shows 2x4x92-5/8" @ $2.00, and your new list has the same item, but at current cost of $3.00, you can update the master list with the new cost. Over time you will develop a substantial cost data base.
As for newly created materials list, you would select the items on the list, and update the cost from the master list. Any exact item in the Master List will then transfer that cost to your new list.
I used a simple plan for this purpose, which has most of the items we normally require for every project.
Also, you'll want to re-visit the "Structural Member Reporting", check the buy list, and add or remove items as needed, and check "Consolidate Unhandled Boards. This should end the materials list reporting 15 pieces of 2x4x3-7/8", and group them into something like 1 Pc. 2x4x7'-8 5/8.
Good luck, I hope this helps.