This is probably the most important thing of all. Hopefully over time it evens out (you miss a few and then get a few you shouldn't have layed) but I try to use the most up to date prices. I actually track the changes in the prices so that I know when each tab I am scrapping was last updated.

You can always pick selections priced under the middle tab $$$ as an alternate way of laying these, just a thought and I haven't tested it.