@bpt1000"...do we not know how much the deficit truly is?"
Yes we know it. It's all around everywhere in the forecasts. LTR has given a graphic about it on its latest preso page 5 in Bell Potter preso. The deficit can get worse but not better than this forecast. (yes it's getting for every year).
The reason it can get worse is this;
the problem is the supply, leave the demand aside which is also increasing.
The supply is tight. That's the problem.
That is also said in LTR's preso;
"Forecast lithium market deficit is expected to grow significantly out to 2030, driven by tight supply. New supply coming from greenfield projects takes between 8 and 10 years to come into first production, with projects globally experiencing permitting, funding and geopolitical hurdles"
We know all the existing mines, the mines under development, and the existing exploration projects. Then we put them all together and the upper limit of supply is definitely known. We can also consider that not all of those project may be in production when the time comes. We know that from the past experiences (I will give you an example below for that too).
More importantly, no new hard rock resources has been found even at the one third size of Kathleen Valley in last 4 years. I made a table longtime ago, 3.5 years ago (below). Updated along the way. When you look at that table you can see that there is even no new resources added in last 4 years. No more than 50mt resources.
The 3 years old graphic below is still valid as well.
Even a new big resource is discovered, it would take 8-10 years for getting into production. Here is a graphic from IEA's (most trustable institution for me) "Global Supply Chains of EV Batteries" document.
Do we know demand?
Yes we do know the lower limit, it's on the forecast tables but we don't know the upper limit. 
The number of EVs sold and the increase in demand for EVs every year give us the annual grow rate ratio.
Also the number of existing, under construction and planned battery gigafactories also give us the demand for lithium. They are already very very high.
The capacity of battery gigafactories in 2031 is now even higher than 7TWh (7,000GW).
Even Goldman Sachs was saying the battery demand was set to rise ten-fold over this decade on its downramping document "GS Battery Metals Watch - The end of the beginning" published couple of months ago.
Also, let's keep this comment in mind as well. From IEA again.
So, what would we expect the spod price be in the next 5 years?
(I'm not interested in next 10 years)
SC6 spod price is now over $$7.500/t.
LTR's ave. LOM spod sale price was around $1,400/t on DFS.
I/m happy with ave. $3,000/t spod price for the next 5 years. Still more than double of price on PFS. That'd be enough to make LTR a blue chip stock.
(20min delay)