PSC Compared to Lithium Peers, page-11

That is based on couple things
since the updated DFS,

1. Petalite recovery has nearly doubled with their recovery testing mid 2020
2. Their low iron petalite receives a premium price compared to Spod.

"Petalite flotation is expected to significantly increase Arcadia’s life of mine ultra-low iron
petalite recovery by over 94% compared to November 2019 DFS"

Very huge upside here for DFS, a done deal, just not released yet

Following the release of the Arcadia Definitive Feasibility Study (DFS) in November 2019, Prospect has focussed on improving petalite recovery to meet demand from premium glass ceramic consumers.
December 2019 DFS (ASX release date: 12 December 2019) estimated a project NPV10 of US$710 million, utilising petalite recovery of 31%. The locked cycle flotation testwork indicates significant potential to increase petalite recovery from 31% to >60%, across all Arcadia Project ore bodies contained within the reserve.