Hello. I have been using 2x10s to build bee boxes. They are $12.33 for a 16ft. 2x10 at Lowe's Hardware right now here in Wake Forest, NC. You can make a few boxes out of one board. This construction wood is cheaper and thicker than the thinner wood sold at Lowe's, which beekeepers commonly use for bee hives. I would customize the size of each box to be smaller because the standard 10 frame Langstroth box is very heavy when full of honey. And you would be able to split by the box to make spring splits as Michael Bush wrote about in his book, instead of having to take frames out when splitting hives.
The tongue and groove joint in picture below. Finger joints with nails are not very strong and so the bee boxes fall apart with use. With the joint in the picture below and the thicker wood together make a stronger bee box. Dado blade on table saw works quicker and easier than router.
Because the 2x10 board width is not quite enough for standard Langstroth frames you will need to add a ridge of wood for the frame rest instead of rabbet cutting out the frame rest. You will probably want screws instead of nails for this ridge since the propolise could pull the ridge up with the nails when taking boxes apart.