To elaborate a little bit about my typical needs and wants:

NEEDS:

3" x 4" x 5" box. Not too picky if it's die-cast or sheet metal or
milled out of ingot. Front cover needs a rectangular hole about 2" x
3/4" to let a LCD show through. A couple of square buttons stick
through the front panel. A couple of toggle switches stick through the
front panel. A PCB is attached behind the front panel (where all these
LCD's and switches are mounted).

Internally maybe a transformer. Two D-sub connectors on the sides, so I
need nice D-sub holes.

Back panel has several BNC's and other stuff mounted in D-shape holes.
Also a IEC line input connector (rectangular hole).

I'd happily pay $50 and maybe $100 for something like this fabbed in
single quantities. I might make 2 or 3 orders a year. I'd expect a web
or PC-based tool (for free) to help me specify the order, and a web
order form that'd let me submit an order at 3AM on Saturday night when
the kids are asleep and I have an hour to spec what I want. I'd expect
delivery in a week or so. I'd expect the resulting box to be flawless
and everything within tolerance and all the holes to be "clean".

WANTS:

Painted (powder-coated?) or anodized cabinet and/or panels.

Lettering on front/back/sides.

Internal threaded bosses or maybe slots for mounting PCB's and stuff.

These could add another $30-$100 to what I'd pay.

My standards about what I'd be willing to pay have little to do with
retail prices of existing boxes or what I could hack out with a file
and a nibbler but more to do with what typical prototyping services
(expresspcb, frontpanelexpress) charge per job and a perceived value in
a really finished custom box.
(And a little bit in the cost of specialty punches. I actually have a
couple of D-subs and D cutters that I've picked up over the years.)

Some people will tell you that what I'm willing to pay is too high by a
factor of ten. These are not your potential customers (and I don't
think you'd ever make money by selling to them. No disrespect, I
understand those who don't want to pay any money to have other people
do work for them.) At the same time what I'm saying that I'm willing to
pay is a fraction (maybe 1/4 or 1/8th) what a local machine shop would
charge for a one-off job. I'm not paying because I'm incapable of doing
a shoddy job at putting all these holes in an off-the-shelf box, I'm
paying because I want a really professionally customized box with nice
holes made using punches I don't already own :-).

Tim.