jeremy wrote:

Photographers for whom their lenses are mission-critical are not known for
embracing third party lenses. What do they know that amateurs don't?
Well considering how many people suffer sheeple mentality, I'd say they
care more for the 5 letters emblazoned on the front cap than the glass
quality. I know people who would buy anything with C A N O N on it,
even if it just came out of a dog's butt. But I also know several
working professionals who happily use 3rd party lenses. I know several
who use Tamron 90mm macros and swear by them. One who does a lot of
wildlife work uses the Tamron 200-500, because the overall combination
of size, weight, zoom range and optic quality is better than anything
with the C word on it.
Many 3rd party lenses are just as good or better than the oem lenses.
Even in the budget category, the Sigma budget offerings that get used as
Pentax kit lenses here in Australia, blow the pants off the Canon, Sony
& Nikon equivalents. Move up the scale a bit to the mid end, and once
again the Sigma, Tamron and Tokina offerings hold their own against many
name-brand lenses that are much more expensive. Tokina's ATX-PRO series
lenses are excellent. Sigma's red-ring series and most Tamron lenses are
likewise of excellent quality.
Perhaps as an exercise you should check the specs of some oem-branded
and 3rd party lenses - for example the sony 18-200 and sigma 18-200 come
out as being practically identical except for the finish and price tag -
right down to the weight in grams. Coincidence? maybe. More likely
though that they are identical designs, and possibly even made in the
same factory. Certainly after giving them a bit of a run (admittedly not
a thorough test, but comparing shots taken one after the other of real
world subjects), I couldn't tell any difference in optic quality at all.

I would opt for an OEM's low-end line, or even OEM used equipment, before
messing with third-party gear.
Are you seriously saying you'd opt for Canon's kit 18-55 & 75-300 over a
Tokina ATX-Pro?
I do not see Tokina breaking any sales
records.