My son was showing me some old used Nike Air Jordans (80s, 90s models) for sale on line with asking prices up to 5k. Made me wonder if certain models of running shoes if kept and stored for x # of years would eventually be worth anything? Do you keep your old shoes? My dad still has a pair of Nike Mariahs from the 80s. Doubt they are worth anything and not sure why he has kept them.