Why do you pay more for a lens

So what is the single main reason you decided to pay for times more for an "L" lens ?

Highly dependent on the specific lens, but usually it is for features:

70-200/2.8 II and 24-70/2.8 - I specifically wanted the f/2.8 aperture in these focal lengths combined with ring-USM and, in the case of the 70-200, IS.

100-400 - I wanted this range with ring-USM and IS.

24-105L - The range mostly, plus ring-USM and IS.

16-35/2.8 II - I wanted f/2.8 in an UWA, plus ring USM.

50L - Pretty much for ring USM. I've used Canon's other 50mm lenses and found the AF performance to be inaccurate.

There are no alternate Canon brand lenses for any of the above with the features I wanted. There are some third party alternates (24-70/2.8 and 70-200/2.8 in particular), but I did not choose these.

All of the above.

gonzogolf wrote in post #11968552
All of the above.

Ditto

For me, it's a combination of these.

You can fake a lot of the L lenses benefits if you have a cheaper lens with photoshop (color, sharpness, bokeh, contrast, distortion) but you can't fake focusing speed, build quality or resale value.

+1 accuracy is the most important thing. everything else can be fixed except soft pictures.

sharpness

Sharpness is a no brainer after a while.

gonzogolf wrote in post #11968552
All of the above.

Same here.

gasrocks wrote in post #11968637
Sharpness is a no brainer after a while.

Words of wisdom .

Sharpness - aperture - focusing speed and accuracy - build and weathersealing

Resale is mostly not a concern of mine at all - sure its nice to have lenses that keep a high resale rate, but I'm buying to use not to wheel and deal and sell. Colour is also a little less important since its more easily controlled in editing (plus the other reasons already listed lead to colour and contrast improving overall so its kind of in there as well ).

Of course all the above can come with downsides:
Weight - size

and I'd add them to the list as well as sometimes a more expensive, lighter option or a more expensive smaller option is worth far more to the photographer than having a cheaper; heavier/larger option.

All in all there are many things that go into the choice of a new lens - the primary choice however is that it meets the needs and the budget of the person purchasing the lens.

You missed kudos..... So much more impressive to have that red ring around your lenses...

Primarily for the drawing style, of which the color rendering is a part of. There's more to it however - the micro/local contrast, the bokeh, the sharpness-to-blur transition etc

So my modified list in order of priority would be:

Drawing style (including color rendition)
Aperture
Sharpness
Build and weathersealing
Focus speed and accuracy (I buy mostly manual focus lenses these days)
Resale value

I would pay the extra money for:
1) constant aperture
2) faster apertures
3) full time manual focus
4) free lens hood

Things to come free with those expensive lenses:
5) slightly better image quality
6) different colour rendition - usually for the better
7) red ring - equivalent to a guys engagement ring I suppose
8) pouch
9) extra weight. due to faster constant glass and metal bodies.

Things that do not affect me:
10) weather sealing - because my camera body does not offer it. Becomes redundant it only the lens has it.

Some lenses do not come cheaply. Like the tilt and shift lenses by Canon. Or the super telephoto primes.

I like to pick more then one option.