I think they are being auctioned off/sold for Michael J Fox's charity.
ETA...Yep
Nike auctions off Back to the Future style trainers for Michael J Fox charity
Digital / UK
Nike has announced that it is to sell 1,500 limited edition trainers in the style of those worn by Michael J Fox in Back to the Future Part 2, on ebay to raise money for the actor’s foundation.
Trainers are already selling for $3,500 each, with the proceeds being donated to the Michael J Fox Foundation for Parkinson’s disease, although, unlike the ones worn by Marty McFly while visiting the year 2015 in the film, they won’t lace themselves.
http://www.thedrum.co.uk/news/2011/0...j-fox-charity/