It is much cheaper to build a broadhead archery target than to buy one from the market. A cube-shaped broadhead archery target is stable and does not need a frame to be supported on, unlike the bag form. Since it has six different faces, it provides a larger target area to be practiced on and will therefore last you longer than any other shape. The materials required in building a broadhead archery target are also cheap and easily available.
Using epoxy or any dense glue, join a few cardboard sheets together such that a block of thickness approximately 12" is formed. Make six such blocks for the cube's six faces. Using epoxy attach these blocks together to form the cube's exterior. Lay one block on the floor and join four blocks at right angles to it, one by one. Do not join the sixth face yet as you need to fill the cube.
Stuff the cube with dense foam. Since the exterior itself is thick, this will not take much time or material. The foam need not be in cube form, it merely needs to fill the gaps within the cube to add substance.
Join the sixth face and close the cube. Secure the exterior using packing tape. Place the cube on a desired height by placing it on a stool and shoot arrows at the cube to check its stability. If the target seems rickety, then add more layers of cardboard, followed by packing tape.
Spray paint the cube black (or a dark color). Cut out circles from any remaining pieces of cardboard, dip them in white paint and use them as stencils over the cube. Make a die out of the cube by changing the number of dots on each face from 1 to 6.