I've only ever purchased used/NOS items that are no longer in production. Never bought an item from
ebay that I could get locally, authorized with warranty.
Reason for the low prices is 1) Most items are not eligable for manufacturer warranty, 2) you never know what you are getting....item listed as "new" could be a return, refurb or B-stock item, and 3) always run the risk of being ripped off by the seller (Indoaudio and TheZeb are a prime examples), and 4) having to wait for shipping times, no free hands-on support if you are having problems (like you could get from a local shop), etc etc..
If you are any good at negotiation, you can get gear at your local shop for close to
ebay prices. Atleast close enough for me.....I don't have a problem paying an extra $75 for a full manufacturer warranty and in-person, hands on support if I need it.