I don't think making PCB was ever expensive, perhaps making a professionally looking one.
In old times you had a piece of plastic with a copper layer. You put wax on it, then you could use a needle to remove wax in right places (you basically print the inverse of the circuit)
Place that PCB in acid, and after the copper gets dissolved you clean it up, and have printed PCB.
There are many techniques people have, and modern ones involves printers, but you kind of always could do one at low cost. It might just not look that nice.
Doing a complex 8 layer board would have been traditionally expensive... or nonexistent, depending on how long ago we’re talking. DIY accessible stuff is usually single layer or dual layer through-hole stuff.
In old times you had a piece of plastic with a copper layer. You put wax on it, then you could use a needle to remove wax in right places (you basically print the inverse of the circuit)
Place that PCB in acid, and after the copper gets dissolved you clean it up, and have printed PCB.
There are many techniques people have, and modern ones involves printers, but you kind of always could do one at low cost. It might just not look that nice.