This is my favorite video for rabbit C&C cages. It should be big enough for a pair of dwarf rabbits that get lots of free range time (at least 6 hours a day). If the rabbits are going to spend more time in their cage than the cage should be bigger, at least a 2x5, three high like this one.
Depending on the size, my 2x4x4 with 4 levels was around $80. Depending on if you have wood already depends the price. A full 8x4 sheet is around $20. The cubes are about $20 a box, and if you use dowels which are in most cases stronger than grids and won't make it cave in. Can run you around $8 a piece
I agree those price estimates. You should be able to build the cage for between 100 and 200 dollars depending on how big you need to build it. Obviously if you go bigger than 2x3 for the base you will need two sheets of plywood. I used 3/4" plywood when I built my rabbit cage because it is stronger and less likely to bow. The guys at Homedepot cut the wood for me so I didn't have to. The cage worked really well as a home base for my pair of mischievous mini rexes.