We could debate this until the cows come home (I don't understand that expression. Where did they go, anyway?), but the answer is going to be impossible to come up with because every GM values every player differently.
For those who value this as a 2-player draft, A move from 12 to 11, or even 6 to 5, probably won't be that expensive. But that move from 3 to 2 is going to cost us huge.
Fortunately, some GMs see this as 2-players, others as 3-players, others as even more. Let's just hope that if we have the 3rd/4th pick, the GM at 2/3 sees it as "more." It will still cost us huge that high in the draft, but it will be even huger if the GM we are trading with places a high value on the pick that they are giving up ("a player") and a low one on the one they are receiving ("the rest of the draft").
Mike
ETA: Of course, you could also make the argument that any GM who is willing to trade with us is bluffing. If Philly has the second pick and they think that there are two stars in the draft, they're probably going to refuse to trade with us if we have the third, no matter what we offer (Maybe they accept three BKN picks, but you can see where this is going.). On the other hand, if they think that there are three stars in the draft, all of whom they value relatively evenly (for the sake of simplicity), then the marginal value that they would need to receive to swap 2 for 3 is much less so. But the Celtics don't know that they are largely indifferent between 2 and 3, so they'll try to jack us up, anyway, hoping to get something of much greater value than the marginal difference (to them) between the slots. Thus, if they are making an offer to swap with us, it's very likely going to be much higher than they would actually accept.