Regarding Lowes, you have to buy 8 ft. lengths. That means you waste about 1 1/2 ft. if you have a shortbed.
Home Depot sells by the board foot. I picked the 8 ft. red oak boards I wanted and they cut off 1 1/2 ft.
1x8x6.5 @ $3.95 a board foot
1x6x6.5 @ $2.85 a board foot
They kept the 13 1/2 ft. of scrap and charged me for 6 1/2 ft. for each of the 9 boards. Total savings, $42.54, includes 6% tax.
Needless to say, I was a happy camper.