[davidmanze]

I should add I actually do take chances on used lenses:

Tamron SP 180mm Macro, Tamron SP 90mm Macro, Canon EF-S 60mm Macro, Canon 50mm f1.8 Mark I were all bought used.  They are definitely some of my best lenses, and I got pretty lucky.  I bought them all on eBay, so I can't pretend that wasn't a bit of a gamble. 

 

I also, pretty much exclusively use the grey market to buy new lenses.  (Meaning not from an authorized US distributor). 

 

It is your basic cost to benefit scenario.  It all depends on the price difference.  I can't tell you how many times I see a used lens selling for more than a brand new one.  What are you going to do?

 

 

    The more you write the more I wonder if we are not related somehow, I think pretty much the same way!

Like your "keeps me out of trouble" line. 

 

   Yeah, I take plenty of chances with S/H stuff, but frankly I've had just as many de-centered lenses buying new if not more, you do have the chance to return them though and sellers have changed their policy for the better, many here would only return the lens to the maker, so you bought a lens, tested it, only to find you have a two month wait while it's being seen to. Now I only buy from the big sites.

   I buy mostly S/H fixed focals, you run less of a risk when there are dozens of glass elements shifting position, I can say that nearly all the zooms I've ever bought bar two had some sort of centering issue, new were returned/replaced/repaired S/H were resold usually after I'd packed the bayonet to improve them. 

 I buy grey too, the refund or exchange policy is worth it's weight in gold, four greys now, Pentax K3 (Pentax honored their guarantee) Tamron 150-600 was exchange no problem, D750 and the recently exchanged D500. As you say I'm still seeing S/H D750s for more than I paid for it.

  I won't risk another lens from ebay though, one out three is way too risky for me and the sellers are difficult to contact!

 

  I've just googled the Helios 103, is it a Contax bayonet mount?