The cost of cages can vary a lot, from system and between countries. I live in Sweden and the prices are gives as in Sweden. Sweden is an expensive country, so it might be lower cost in other places.
The cage-system are also designed according to the Swedish legal system, it may vary in different countries. We have more restrictions in Sweden than most of other places so I think the system will not violate laws, but have a check and do the modifications.
To prevent cannibalism among the birds in a country you can not debeek a bird, you must take this in account while construct the cages. This is the reason the cages not have wires for the birds to walk on, and the minimum area for a normal-sized Coturnix is set to at least 160 squarecentimeters. Even then a cage-rack which can hold up to 175 birds it will not require more than 3 squaremeters floorspace including the work-area around. I can hold 1750 birds in my garage of 29 squaremeters after I have installed proper ventilation.
The prices for the cage-racks are about USD 190, which is about a dollar a bird, and I estimate I can use the cages in 10 years, it means the cages cost is about 10 cent a year for each bird. It takes just a few hour (at most) to assemble a cage-rack.
Each rack has seven stories of cages with a floor area of 4000 squarecentimeters, suitable for about 25 birds, given them 160 squarecentimeters each. In areas there you do debeeking up to 33 birds are maximum, but 25 is still optimal.
The skeleton of the racks is a Sweden-invented thing, a product of IKEA, which have designed
a furniture for store books and other thing. The Ikea has warehouses almost all other the word,
but if you not have access to the product, you can for sure find a simular or make one.
So the shelf-system called "Ivar" you buy peace by peace as you want it. In our case (something the IKEA designers for sure not thought about) we buy two sidepieces of 225 cm height and 50 cm deep, and then 8 shelfes 80 x 50 cm. The price in Sweden is USD 80 (I have excluded our high 25% salestax as no other countries pay tax as we do).
It is good to paint every part before putting it together with a glossy paint, it will make the enviroment less attractive for parasites, and easier to clean.
Follow the instructions for the "Ivar" (no tools are needed) and start from the upper put the first shelf att the uppermost holes, and then the other shelfes in every ninth holes, which will give you seven spaces of 4000 sqcm floorspace and 27 cm heigth.
Buy four meters of welded wire with about 12 millimeters space and at least .5 millimeters wire thickness, the price here is about USD 14.
Use two meters of the wire to cover the back of the cage-system by nailing it on. It will at the same time make the rack stabile. Nail to the shelfs as well.
Buy 14 pices of plywood of between 6 and 12 millimeters thick at the size of 50 cm by 27 cm (check the height between the shelfs it can be 27.5 or something depending of the system of the holes in the sideracks) and paint them. The prices are about USD 20 for all 14.
Buy from a workshop seven metal plates of the size of 79 cm by 66 cm and thick so it feel steady. The plates should have an anticorrosive surface at one side. Let the workshop bend the plates on the long sides 90 degree and 8 cm in on both sides with the anticorrosive inside. (Price is USD 25).
Place the plates one on each cage-floor and press the plywoods towards the side-racks on both sides.(No tools needed).
Buy a box of clippers which use to be used then nailing electric wires to walls, take the smallest you can find.(prices a few USD).
Make 14 peaces of the rest of the wire in size of half the distance from the left egde of the cage to the rigth egde and about 22 cm in heigth. It will be doors for the cages.
Use the clippers to nail the doors against the shelfes so it will be opened upwards.(a wire-siccors and hammer is needed).
Buy 28 plastic feedtrays which can be hocked outside the cages.(prices 1.3 USD each). They should be about 25 cm in width. Cut holes in the wires close to the egde of the plates by making it 4 times the wire-holes or so big the birds easy can put the head out and eat but not escape. Hook the trays at the holes and to the plates at the same time and you have a lock to the cages at the same time. Make holes for watertrays at the backsides.
Use the backsidetrays for water and the fronside for dry food. Put litter in the cages and check everything over, then you are ready. If you can effort and have space use only the six lower cages regular and the top when you temporary need more space as it needs a ladder to manage the top cage. If your roof is too low the side-racks can be obtained in other sizes for less cages in the rack.
I know it can be hard to understand instructions written by the person who already knows, it is easy to forget explaining things the writer takes for granted, so you should not feel stupid because the instructions may be it. I have taken some pictures of my cages to make it easier to see. You are always welcome to mail me for clearing out things I have been less particular of at firstname.lastname@example.org I will try to assist you if you reach any problem.