I'm looking to get a 1.8 50mm lens for my Nikon. Shopping around I'm seeing all these different prices. Any advice?

I found these
http://www.adorama.com/NK5018AFDR.ht...FRGqnQodkn0AzA

refurb

http://compare.ebay.com/like/2307440...Types&var=sbar

This just looks old

https://www.google.com/search?q=1.8+...w=1185&bih=642

overall search page I'm looking at right now. Thanks people!