As with guns, fountain pens, cameras, watches and all the other stuff I seem to amass, I buy both new and used. Moreover, the items I buy get used: they are well cared for and not subject to abuse, but don't spend their lives in drawers or display cases.
That said, I seek used knives that have actually been used if the price reflects this, and the knife has not led too hard a life. Naturally, it's always a delight to come across a pristine offering at an exceptionally good price, but ours has become a sellers' market, so such opportunities are rare.
There are, of course, some high-end knives that command a premium over their MSRPs in the used market. Several have caught my eye, but personal economics dictate that I get on waiting lists where that is an option, as well as regularly cruise vendor and manufacturer websites looking for the latest drop.
Such is the nature of an artisan driven market.