On Fri, 09 Dec 2011 13:34:34 -0500, Bob Engelhardt
wrote:

If cheap is your only requirement:
http://www.dealextreme.com/p/analog-150mm-caliper-6199
...

The problem with that one is it's 2mm per revolution.

If you need so great resolution that 2mm per revolution is a problem,
you must stop looking for cheap options. The dial is marked for every
two hundredths of a millimeter, and you can easily see when the needle
is between two marks, so you can interpolate to the nearest hundredth
of a millimeter. The indicator, however, is sloppy enough that two
successive measurements on the same object can differ by a hundredth
or two.

The bar is marked
in cm with 4 ticks between each.

No, it is not. It is marked in cm with 9 ticks between each, such that
each tick represents one millimeter. Also, the half-cm tick is a
little longer than the others, so you never need to count more than
four ticks.

So to get the mm you have to count
ticks, multiply by 2 & add the dial reading.

No, you don't. Just read the number of ticks off the bar and then read
the decimals off the dial. As an added bonus, you can use the dial to
verify that you have counted the millimeter ticks right: If the dial
is in the left half, the millimeter count should be an even number,
and if the dial is in the right half, you should have an odd number of
millimeters.

High resolution, but a
nuisance. I'd rather rather have one with 1 cm per revolution.

As mentioned, it would not make sense. There is no point in having
much better resolution than accuracy, and with the accuracy you get in
this price range, there is no point in having 10 micron resolution.
Even the 20 microns is somewhat excessive.
--
RoRo