Ann: Scoping Study Reveals Exceptional Economics-Ngami Cu Project, page-71

So drilling wells is somehow more expensive than drilling an open pit mine or (miraculously?) an underground mine??
The SS noted that they're running the pilot plant in years 1-3 and it pays for itself in 0.85 years. In year 4 the full scale production is built and it pays for itself in 1.69 years and that's on the most conservative copper recovery of 30% VERSUS a payback on the Pilot of 0.23 years and Full Scale of 0.64 years, if copper recoveries are at 60%. Still waiting to see the actual scoping study on CBEs website but assume its going to be released soon.
In terms of commercial recoveries see a few examples: "San Manuel “in situ” mining in Arizona reported copper recoveries in the range of 50%–60% over a period of 5 years. Copper was recovered through this method at ASARCO’s Silver Bell Copper mine in Arizona from fragmented ores. Even recoveries as small as 20%–25% is believed to be economical." link: Situ Leaching - an overview | ScienceDirect Topics