This has been discussed in many places on this forum. Please search/read through other threads (as the rest of us have done). Anyway, It all depends on where you do it. RS has said $100 off the 3D if you trade in the 4G, but they'll give you around $120 currently. Sprint supposedly will buy it back from you, but the numbers I've heard vary, so I won't comment. I think Amazon will buy it back too, but again, I don't remember how much they'll give. Try reading through some of the more popular threads here. I'll post later if I can find it.
