The doors were mastered as two parts - front and back. Single-part moulds are a piece of cake to make and cast. All you need is silicon and some resin or plaster for casting. Whilst it's cheap per part in theory, the initial outlay for materials will bump the cost, so bear that in mind.
I've taken to making masters for single part moulds directly on a base sheet of styrene. Once you've done, cut around the master leaving 10-15mm around the edge of the base. Cut some sides from the styrene sheet that are taller than your master and simply tape them to the base making sure there are no untaped gaps for silicon to escape through. Mix your silicon and pour it in your mould. Once the silicon has set, you're ready to cast
Here is a mould box and parts immediately prior to casting:
I'd definitely recommend having a go as it's a really useful 'tool' to have in your kit. Good fun too
