There is no one answer to that question, it is likely different for each person and even when someone does decide what the answer is for themselves it maybe years or impossible for them to know if they made the correct one. Unfortunately in peejaygee he may have gotten ripped off, which is very hard to factor in when deciding how much to pay for a used product. Even if he didn't get ripped off how does one factor in that a used Series 3 could die with in days and not be repairable? On the other side of the coin a used Series 3 could last for years with no issues. So no one has enough data to be certain they are making the "correct" decision, which is why there is no "correct" or "wrong" answer to your question. If you look at cars I can tell you I have a car that is 5.5 years old with 45000 miles on it, it currently is worth about 1/3 of what I would pay for a new one (same model and options - yes I have been looking ). I am certain my car has more than 50% of its useful life remaining. If I assume a Series 3 has about the same amount of useful life remaining as my car then maybe it should be selling for about a third of a new model given that a new Premiere with lifetime is $600 for anyone then I would put the value of a Series 3 with lifetime at around $200. But again that is just me.