This is a wooden rack I built to store 5 of my bicycles. It is constructed of 2x4 and 2x2 lumber assembled with glue and screws and the shelves are nailed on with steel framing brackets. The total cost for materials was about $25 and it could be built even cheaper if you can find 2x3 lumber or you have some of the materials already laying around your workshop.
The upper bicycles are bungee'd to the rack in case of earthquake or Godzilla attack but really they stay pretty well without the straps.
Please let me know what you think about the rack. I'd be glad to answer any questions you might have.