I needed an acrylic display box for my anime figurines and i thot it would be cheaper to make my own.

What you'll need:
* 11x17" acrylic sheet (2) $3.57 x2 = $7.14
* sharp razor blade/knife
* metal straight edge (ruler)
* self-healing mat
* Legos
I bought a plastic sheet cutter ($3) but it turns out it was nothing special and a razor blade knife would've done the same job. Just make sure it's sharp and has a nice handle. So really the cost is only the acrylic sheets since the other stuff i already had.
I decided to split the sheet right down the middle for a box height of 5.5" and make a width of 4" for the side pieces (length 17-4 = 13"). In retrospect, it would've been easier to make both the box height and width 5.5" because then the front/back and top/bottom would be the same size and there would be less cuts to make. It's pretty easy to cut acrylic sheets, basically you score a line and then break the sheet across a hard edge.

I needed a frame to make sure my walls were 90 degree angles from each other and the table, so i borrowed a trick from
casting plaster and used Legos to build an inner and outer brace to align each corner. A bead of hot glue along the outer edge. Repeat x3 more times for each corner. The 4 walls should be fairly free-standing now. Then I hot-glued the outer edges that were previously covered by the Lego frame. Use a spot of hot glue for each inner corner to secure the top to the sides of the box. Done! (the bottom piece doesn't need to be glued to the box).
I'll probably use some brush-on Crazy glue (cyano-acetate glue) to fill in the cracks between the top and sides if i want to make it air-tight.
Is this worth doing? Well, if you can find your display box for $8 or less, you might as well buy it. Otherwise, the DIY approach lets you customize the box size and it's actually pretty easy to do.