Prices vary from my region (California) so take a look at these prices which seem to be in line. Note that western red cedar is a better quality structural wood and may be more. Either cedar is fine for your project and will have a nice fragrance.
Lumber is typically sold in board foot price. A board foot is 12" x 12" x 1" or 144 cubic inches. As an example you can calculate board feet for a 2 x 4 x 8' as follows:
2" x 4" x (8'x12") = 768 cu in / 144 = 5.3 board feet. At $1.00 per board foot that board would cost $5.30.
Not much of an answer. Maybe someone back East will have a better idea of a local supplier and prices. Where are you located again?