WHY PHILA DO IT:
As of talent, aside from Simmons, they lose nothing: they don't give up Curry, not even Maxey or Thybulle, but they "pay" with picks (and a player who's a nobody for now). Honestly, the price is not that high for them: swaps will likely never happen and 2022 draft is in 7 months, they can afford losing a rookie right now. The real sacrifice is the 2028 pick, when you don't know what your team will look like. But for Jaylen Brown It's worth it IMO.
They DO NOT pay luxury anymore and won't pay it next year too if they want. Just in time for Embiid's supermax starting in 2023/24.
Starting 5: Maxey, Seth, Brown, Tobias, Embiid
Second Unit: Milton, Thybulle, Green/Korkmaz, Niang, Drummond
WHY RAPS DO IT:
For Siakam they get 3 firsts, 2 swaps even if they will likely not happen, a 2021 first (Springer) and Grant Williams, who started the season shooting 50-40-85. Horford is only half the money guaranteed next season + Dragic out, they have a lot of cap relief.
Core: Scottie, GTJ, OG, Precious, Williams, Springer, Banton, 2022 lottery pick + 2 more firsts.
WHY BOSTON DO IT:
Brown + Williams + 2022 pick = Simmons + Siakam
They take advantage of the situation and get 2 all stars at the price of 1. They accept to pay a lot of luxury for this reason, not every day you can do that.
Starting 5: Smart, J-Rich, Tatum, Siakam, Simmons. Not counting Schroeder long term because he will at least looking for full MLE next season and Celtics won't have it.
Siakam - Simmons, IMO, would be a terrific duo.