PLS chart, page-6848

What are you talking about? The mine was developed on the basis of long term spodumene prices far lower than $800/t. See below from the stage 2 DFS where they forecast a life of mine price of US$633/t
No existing producer will cease operations at US$800/t because they wouldn't have got themselves into production if that was the case.
And I'm not sure why you mention brine extraction operations going bust in relation to a spodumene sales price of $800? Different kettle of fish entirely.
I don't claim to know what lithium prices will do between now and 2030 but my expectation is they remain at incentive levels - high enough to encourage investment and expansion in the sector, but you won't find many DFS reports using figures north of $1000-1200. Truth is no one really has much of a clue - GS are spruiking sudden price crashes this year, but with little evidence to back it up. Producers are saying they are seeing strong demand in the meantime and prices will stay high for the short to medium term, yet a few years ago they were only expecting pricing in 2022 to be sub $600/t, rising to $650ish later in the decade (see below from PLS in 2018).
My point is, if it was attractive enough for current producers to get into business based on a long term price of $600-800/tonne then it will be for many others too until the market finds a balance. And that balance will likely be sub $1000 in the long term. New mining sources and extraction methods like clay, direct extraction of brine, lepidolite etc will only serve to drive down costs and increase availability over time. There's plenty of lithium out there, just takes a lot of time and investment to develop new mines.
Personally I think over the long term the GS forecast is probably quite accurate, but their short term analysis is a joke, and aimed purely at spooking the market, which they very much achieved.
Make your own assumptions and DYOR but my original point was just to caution against assuming long term prices in the $4-7k bracket are sustainable and projecting share prices on that basis. I bought into PLS with an average sub 40c and was mostly sold out in the low $3s, now back in as I can see long term value at these prices. Perhaps I'm being overly cautious, but I would rather that than broke.