It's a one time cost though as they can be reused year after year. I have not tried making them myself yet although I have a roll of the fencing in the garage.

I made a some out of 1" by 2" fencing. They are surprisingly handy for all of the reasons Mel states. I'll be making more.

could you just use chicken wire? around here it can be bought $8 for a 50' roll. that should make more than a few cages.

I don't know that I'd use chicken wire for the cages--flimsy and the hex shape doesn't lend itself to the square edges.

I used 2x4 inch dog fencing for very good results.

Here is a link that might be useful: Simple Mel's Cube instructions

I found that the fencing was much cheaper at the local farm supply store than Lowes or Home Depot. If you have one in your area, its worth checking into.