Cast Urethane and Injection Molding

[BrandonWagner]

I'm in the process of building a metal prototype and looking ahead to production options in plastic.

Considered getting a 3d printed prototype to make the mold for cast urethane, but that technology is still too expensive. Got an estimate of 5k for drawings and 10k to print it.

With that said, my plan is to use the metal prototype to create a urethane cast.

The product is approximately 48" x 30" x 8". Similar structure as a milk crate, but designed for a specific purpose.

Is this too large for cast urethane?

How expensive is a cast urethane setup for a small shop?

Is cast urethane even an option for a product with similar structure as a large milk crate?

What is the general process for getting a product from prototype to injection molding? I assume the only option is letting someone else manufacture with very high upfront tooling cost?

I would like to make 50-100 "milk crates" and go from there.

[Timsmith]

Injection molding = high dollar dies and tooling cost
Is finished product going to be aluminum, plastic?

[BrandonWagner]

finished product is all plastic

[Timsmith]

If it's 8" tall, plastic is cheap. CNC router for about 10k . Do it in your garage.

[BrandonWagner]

I've helped with cast urethane, but have zero CNC experience.
10k is doable especially with the asset value.
Is the programming dumbed down enough for a civil engineer to figure out with youtube/google/scducks?