Because every NBA team generally has significant debt on their books and there are additional operating expenses that need to be covered.. Specifically, the Warriors are self-financing a $1.4B arena, if I’m not mistaken. No idea what the terms on that debt are, obviously. They also have access to NBA credit lines that they may have drawn on during the run up of their Curry era.
Like I said, this team can likely cover in the short-term it but most people have no idea about what NBA books look like (not suggesting you don’t). I’ve actually reviewed financials from a prominent NBA team and it wasn’t as rosy as most would expect. Obviously, the Warriors are a bit of an outlier here with their revenue streams. They have squeezed a ton of money out of Silicon Valley millionaires.
It’s sustainable in the short run, it’s not in the long run. At some point, they’ll rein it in
As another example of this, as far as I know, the Packers are the only major professional sports team that has to publish their financial information on account of actually being a publicly traded corporation. The Packers are a bit of a unique organization, but likely aren't some sort of aberration, and in FY2019 and FY2020 they spent more or less as much on players (243 million and 226 million, respectively) as they did on other things like marketing, coaches, and administration (234 million and 210 million, respectively). I would imagine that, compared to the NBA, NFL teams incur proportionally greater support costs if for no reason other than having rosters more than four times the size of those of the NBA, but it's illustrative of a reality that should be fairly obvious, namely that major professional sports franchises have expenses that go well beyond mere player salaries.
For Golden State's level of spending to be sustainable, that spending is going to have to translate into wins that get butts in seats, specifically Silicon Valley butts. Curry's game will age perfectly well, but he's still 33 while Thompson is 31 and has repeatedly suffered major lower body injuries. Now, if Thompson can be his old self this year, they'll be fine, and their strategy of spending right now when they still have Prime Steph Curry is exactly what they should be doing. Still, it's a window that economically won't be open forever, unless maybe Wiseman really develops into a dominant big man.
There are still plenty of moves that can be made to clear up space. We aren’t going into the season without a starting PG and splitting Smart/Pritchard/Dunn. That would be foolish.
There are, certainly, a few players on the roster that probably aren't worth keeping around and could be safely taken out behind the shed to prevent a nominally 10 million dollar contract with Schroder actually costing about 25 million, but giving up picks to dump Carsen Edwards on someone because you don't think Marcus Smart is a starting PG seems foolish as well.