I bought 2nd hand helmets on Ebay and was not disappointed; just get pictures, history and see what the seller is like with his rating and membership.
I have 1 SPH4 XL White owned from new, a 2nd hand refurbished SPH5 XL White, and a HGU56P M white, all 3 for sale, as I now only use my ANR DC H20
Cheers
WLM