Whiskeyman - Go on...do it! You won't regret buying a Plena!!
It's funny - some lenses on the used market are a TON cheaper than Nikon's refurb pricing; others are the opposite.
Example: Nikon AF-S 105mm f/1.4, easily had for under $1k used, but Nikon refurbs are $1440
on sale.
Counter-example: Nikon Plena is rarely found for under $2k used, yet is $1800 as a Nikon refurb
on sale right now.
These market distortions are strange, but once you figure them out, you can hone in on the best way to purchase a great lens if you can't afford (or don't value) buying new. This assumes you are ok with refurb or used - both have risk. In my experience, the savings make self-insuring for issues pay off, especially for multiple purchases over enough time.