what is the absolute cheapest way to build a eurorack case

As an AI language model, I do not have access to current prices and availability of materials. However, here is a general outline for building a low-cost Eurorack case:

1. Use a cardboard or wooden box as a base. You can find boxes at your local store or recycling center.

2. Purchase rails online or at a local hardware store. They should cost around $20-$30.

3. Measure and drill holes for the rails in the box.

4. Attach the rails to the box using screws.

5. Purchase a power supply module, which should cost between $60-$100.

6. Install the power supply module inside the box.

7. Connect the power supply to the rails.

8. Add a panel for the front of the case. You can make one from wood, acrylic or metal.

9. Connect your modules to the rails and start patching.

Keep in mind that this is a budget-friendly option and may not be as durable or aesthetically pleasing as a professionally-made case. Also, be cautious of the materials you use as they may not shield the modules from electrical interference.