I'd say it all depends on how complex you want your sets to be. I did this in literally 5 minutes using a few bits & pieces I had lying around:
A cardboard box for walls with a sliding door cut out, a cardboard tube for a ventilation duct and some film cannisters for barrels. And I drew a control panel for the door using felt-tipped pens, not that you can really see the the coloured buttons... If there had been any kind of planning involved, I could have used some paint on various parts to make it even better. But to set the scene I wanted, I was pretty happy. I even kept the "walls" for later use:
This time I used a metal baking tray for the door and a cereal packet for the floor. The crate is an example of scenery/props that took a while to make but was really cheap -- it's popsicle sticks (bought at a party supplies store) cut and glued together. I worked shoe polish into it with a toothbrush but I'm not overly-happy with the colour; I'm making more that I'll leave as-is or try and find a light brown polish.
So hopefully I've shown that you can do and/or spend next-to-nothing to at least get across what you mean -- if I had more photography skills I could probably get even more out of those sets. I do have intentions of creating a full-blown dio-story with interior as well as exterior scenes, so maybe we'll eventually see what my lazy arse comes up with if that comes to pass...