So what's the best they can get if they do trade him (presumably based on some level of historical precedent)? That's what I'm asking.
What historical comps are there to a trade of a young rising star with two ECF appearances under his belt already, locked up on a new long-term contract? Kyrie coming to us seems fairly close... ish. Kyrie was a better player with more on his resume than Tatum has right now, but with less years left on his deal - and he was already known as a malcontent, though he hadn't yet gotten as bad as he is today.
We shipped out Isaiah Thomas, coming off of a year in which he dragged us to the ECF and placed 5th in MVP voting, but with a concerning hip injury... the 2018 Nets pick that was a premium asset with top-of-the-draft potential at the time, but wound up merely 8th... Jae Crowder, a solid roleplayer and culture-setter... and a throw-in project big man in Ante Zizic. It's worth noting that the Cavs struck out on pretty much all of those pieces, but that has no bearing on the value they had at the time of the trade.
So where does that get us? As I mentioned, Kyrie was a better, more accomplished player at the time of the trade, though Tatum's better contract and better apparent attitude do narrow the gap some. That's about as close as I can remember. Pieces like Tatum don't move very often.
Maybe loosen the proxy a bit? On the high side, trades like Davis, Leonard, Harden (to the Nets), and maybe Chris Paul (to the Lakers more so than the Clips); on the low side Kyrie, and Harden (to the Rockets).
None of these are perfect comps -- far from it. Davis and Leonard were better players, but NOP was hindered by having to deal with the Lakers, and Kawhi was expiring. But at least these various players are as good-to-better than Tatum, and in their respective primes.
Sadly, many of the players I'd hope to get for Tatum are better (or have higher potential) than B Ingram, who is arguably the best established player traded in the hindsight deals noted above -- assuming you agree DeRozen would be seen as a little less "valuable" considering his age. I suppose the combo of Ingram, Ball and the 4th pick in the draft (plus more picks and change) is pretty good return considering NOP was pigeon-holed to LAL..... of course they basically bungled it from there.
I haven't had a chance to dig through all the picks that were made out of these deals....