iPhone 4 owners are starting to sell their used units as Apple prepares to announce its predecessor. It's a common practice -- sell the "old" tech to help finance the new -- and one Boston-based electronics retailer is already experiencing a significant uptick in smartphone trade-ins and iPhones being offered for sale.
Gazelle's Anthony Scarsella says the current iPhone sell-back is "much more aggressive" than it was when the iPhone 4 was released. Scarsella told The Street that 4,500 people tried to sell their iPhones last week, an increase of nearly 30% from the prior week. If those rates continue, he expects Gazelle to see more than 20,000 customers try to sell iPhones t
