It's because of the simple fact that the first one is Rondo alone for that package while the second one is very far from being only Rondo.
Throwing in AB is probably the worst part of the trade. AB not being as effective as Rondo is a terrible reason, in my opinion, to add him to the deal as sweetener.
AB might not even be starter material. But a 22 year old with playoff experience and all-NBA caliber defense is, in my opinion, quite valuable.
So it stems from an over-valuation of Avery Bradley as a defensive role player with limited offensive ability. Got it.
Either way, what I see at work here is something that's very familiar around these parts -- Celtics fans tend to drastically over-value Celtics players and under-value players on other teams unless they are stars (especially stars that the Celtics have faced in the playoffs).
AB may not be a starter but I sure as hell value him over Jason Thompson or Isaiah Thomas. Just because he won't be as productive without Rondo doesn't diminish his value.
You "throw him in" when you could really just keep him as trade bait later or as a contributor somewhere down the line.
I get a sense that you don't think AB will improve a single iota. AB is 22.
On the other hand, Isaiah Thomas is 24 and 5'9 while Jason Thompson is 27.
Even if AB does not improve one bit, it's not inconceivable, heck, even almost certain, that he will continue to be productive far longer than Thomas and Thompson making him a lot more valuable than the two.
Jason Thompson and Isaiah Thomas are run of the mill role players. A decent big with size but without much skill and a solid, efficient, effective, undersized backup point guard. I reckon AB is at least a couple steps above them, a very young player with a valuable skill that many would-be contenders and contenders would love to have.
I think on all fronts, AB is a more valuable asset than the players the Kings are giving us. You seem to be implying that AB is a highly interchangeable and replaceable, albeit nice, asset with little value, which I must insist he is not.
Then you throw in a 2014 first. I think it's pretty much universally agreed upon that the 2014 draft is stacked as hell, and factoring in Ainge's drafting record, it's a good asset.
As others have mentioned, the hypothetical King's pick may very well be lower with Rondo playing for them. As stacked as the Nets are, they're old and injury prone, making coasting to the post season and ending with a far worse standing than the projected 1st or 2nd in the EAST (and factoring in Western conference teams, the drop could be significant). The move up could be insignificant.
Lastly McLemore is a lottery pick in a top-weak (and overall weak) draft. His stock also fell considerably during the draft, which should raise some questions.
We won't get top of the line prospects, but McLemore is not only not top of the line but possibly damaged goods (for the lack of a better phrase. I apologize for referring to another human being as "damaged" and "goods").
My opinion is AB might be the worst part of the trade as you use him as a "throw in" and "trade lubricant" because he would be less productive without Rondo.
But that is not where my dislike for the trade "stems" from.
I look at it from the standpoint of overall value and I think it's a loss for us.
I am fine with the premise of Rondo for a lottery pick (or equivalent) + decent prospect (+ a little more sweetener). I think it's fair for both sides. But in the proposed trade we're surrendering AB and a decent first round pick.
I feel like your valuation of Rondo and AB is skewed by your insistence on being "more objective and realistic than your average Celtic fan".
I reckon Ainge has quite a bit more leverage than you seem to think. Rondo is no LeBron or CP3 but his contract is a bargain and can definitely be a large piece of any championship puzzle as a contributor.
I don't think Ainge will be too worried at all about being unable to "get rid of" Rondo, throwing in good assets just to sweeten the deal in hopes that the other team will accept the trade like in the Kings trade. I think Ainge will drive a hard bargain.