Worms farms are pretty simple pieces of equipment.  You have a few
layers of trays where you put your veggie scraps and worms, separated
by a perforated mesh that the worms can move through.  The top and
bottom are sealed to keep the worms in and insects out, while
collecting (very fertile) liquid at the very bottom.  You fill the
bottom tray with scraps, then move on to the next tray up.  When the
worms are done with the bottom tray, you empty it into your garden as
wonderful compost
and soil improver, move that tray to the top and continue.
Most worm farms are made out of molded plastic.  The structures are
very simple.  The material is cheap.  The Chinese manufacturing
miracle should be able to churn these things almost for free.
Thing is, the cheapest I've been able to find is $65 from The
Watershed, run by Marrickville and Sydney councils.  At Bunnings
the cheapest is about $80, yet you can buy a Mitre Saw, full of
complex machinery and electronics, for $30.  Someone, somewhere is
making a lot of profit on these worm farms.
If anyone out there has any expertise in plastics moulding and mass
manufacturing, there's a lot of money to be made undercutting these
price gougers.
One option is to make your
own, but it shouldn't be so hard!