I want us to celebrate excess in this thread, so keep 'em coming! I don't think a luxury item has to be objectively expensive, simply that there are completely usable alternatives which might not quite as nice or pleasing to the potential owner.

It could also something that, once possessed, no longer has the owner wanting to upgrade further. With Oakleys, I went through much cheaper options until I finally pulled the trigger and never looked back. I went through the same thing with lights (still surprised when I rustle through my disorganized bike junk pile to find lights that I forgot buying), though lighting keeps improving so there's always something better on the horizon to consider.