The cheapest would be the stuff that people give to you. Old foam mattresses can be cut down to fill the pit, but you'll need hundreds of them. Plywood, OSB would do for the siding. Probably not particleboard or MDF though, not enough moisture resistance. You could try asking at a recycling centre or a demolition company if they can help you out.
The cheapest yard signs are the ones you can make from materials you have at home. These include leftover pieces of card stock, pens, and colored markers.
The materials you could use to make a model of a solar eclipse are:Small appleLarge handful of clayTwo pencilsNotebookPencilLamp
Red is the cheapest color to make.
You have to buy flexible plastic hose, there is no way you could make it, even with the correct materials.
One of the cheapest materials for making clothes would be cotton. Alternatively there are many synthetic fibers which are used to make cheaper clothes.
A table could be made from: metal, glass, wood, plastic, or a combinations of materials.
Some companies do recycle products. However a manufacturing company's first concern is to make a profit, so it will acquire its raw materials from the cheapest source. With materials still being plentiful, companies are often in the position that they have to use virgin materials as they are cheaper.
5 robux. that is the cheapest you can make a shirt.
chocolate probebly
Ice and snow if you live in Nunavut!
you could put alimunin in the circuit
One can make a brooch using many different materials including fabric or plaster. Looking in a crafts store could lead one to find simple materials to use.