Another option is simply not using plexiglass on a DIY cage and doing the Walmart tables I mentioned for a 40 x 40 cage with mesh and 12 inch high substrate borders.Then,the only cost aside from tables and mesh would be a sheet or two or melamine(depending on what size you find to be the cheapest since it will need to be cut regardless).For substrate borders,you can probably make them out of cardboard and that makes it cost far less!With that sort of idea,you could probably make a square meter DIY for less than $75 which is half the cost of a double Detolf and only a bit more than a single Detolf(but a more suitable amount of space).
By the way a 4 ft x 8 ft melamine sheet is only $30 at Home Depot,and half inch mesh is around $15 or less!If you can find cheaper sheets of melamine as well as cheaper mesh that is the same type but a smaller roll,the cost would probably go down.Either way it's a lot less expensive than making a double Detolf,but still around the wonderful square meter size