You get what you pay for when it comes to dental labs.  Pay the
lab a fair fee and you're most likely to get good work.  Remember
that a re-impress of a crown can result in the profit on the crown
going out the window.  If a lab is constantly returning things that
don't go in, deep six the lab.  The psychological and overhead
costs of useless labwork are high.  $39.00 seems very low for
a crown.  Maybe the lab isn't using gold or white gold for the
crown, or maybe they outsource to some poor unmotivated
drudge working for $1 a day in some east asian country.  Maybe
they are using cheap materials.  They must be doing some
shortcut to make it cost-effective to offer crowns for that low.
Best advice on labs: don't work with labs that do sh.t work.
Pay a slightly higher price if that will help ensure a higher rate of
success, better quality control, better esthetic result, and better
customer relations and support by the lab.  A re-make on a
crown will cost about 1/2 hour of chairtime (at $4 a minute) plus
$50 for re-impressing, plus the cost of psychological frustration.
You quickly hemorrage money if the lab you work with gives
you an even slightly higher rate of failure.

Think about it: a quality lab technition should be as smart as
possible, with lots of common sense and as much liberal arts
education as possible.  People like that don't work for sh.t
wages.  You have to pay them well for them to keep doing good
work and keep being motivated.  That means higher costs
per crown.  If you go for cheap crowns, the guy who makes them
might not have enough personality to do a good job.