*Your "back of the napkin" breakdown is actually very reasonable...

*Your "back of the napkin" breakdown is actually very reasonable for an early-stage analysis. Here's a step-by-step verification with added context and minor refinements:

1. Resource & Revenue Estimates

Deposit:

• 681,000 tonnes @ 2.8 g/t = 61,300 oz Au (as per the MRE)

Gold Price Scenarios:

• AU$4,000/oz → AU$245.2M

• AU$5,000/oz → AU$306.5M

✔️ Your estimate of $244M–$306M in revenue is accurate.

2. All-In Sustaining Costs (AISC)

You assumed:

• AISC = AU$1,500/oz (sensible upper end for small-scale WA open-pit ops)

Total AISC cost =
61,000 oz × $1,500 = $91,500,000

✔️ That checks out. This is reasonable and covers mining, processing, royalties (4% noted in the report), sustaining capex, rehab.

3. Capital Expenditure (CAPEX)

You estimate:

• AU$150 million CAPEX midpoint for a shallow open-pit.

This is on the high side if:

• They go with toll treatment at a nearby mill (which the company is exploring).

• The mine is modest in scale (681kt) and already on a granted lease with highway access.

Alternate low-CAPEX scenario: If toll treatment is used, CAPEX could be in the $20M–$40M range (mostly mine development, contractor setup, approvals).

✔️ But your $150M figure is appropriate for a conservative standalone scenario.

4. Net Profit Calculation

At $5,000/oz gold, with:

• Revenue: $306M

• AISC: $91.5M

• CAPEX: $150M

Net Profit = $64.5M

✔️ Spot on with your formula. And that’s conservative since you use the higher AISC and mid-to-high CAPEX.

Sensitivity Note

If they:

• Reduce AISC to $1,200/oz → cost = $73.2M

• Use toll treatment → CAPEX = $30M
  Then profit could rise to ~$200M+ depending on terms.

Summary

Element	Your Estimate	Assessment
Revenue	$244M–$306M	✔️ Accurate
AISC	$1,500/oz	✔️ Reasonable upper bound
CAPEX	$150M	✔️ Conservative standalone case
Net Profit	$64.5M	✔️ Realistic base case

Your calculations are valid and well-reasoned.

Here’s a sensitivity table showing how net profit varies based on different assumptions for gold price, AISC, and CAPEX.

You can quickly spot how higher gold prices or lower costs impact profitability.

Gold Price (AUD/oz)	AISC (AUD/oz)	CAPEX (AUD)	Revenue (AUD)	Total AISC Cost (AUD)	Net Profit (AUD)
4000	1200	$30,000,000	$244,000,000	$73,200,000	$140,800,000
4000	1200	$75,000,000	$244,000,000	$73,200,000	$95,800,000
4000	1200	$150,000,000	$244,000,000	$73,200,000	$20,800,000
4000	1350	$30,000,000	$244,000,000	$82,350,000	$131,650,000
4000	1350	$75,000,000	$244,000,000	$82,350,000	$86,650,000
4000	1350	$150,000,000	$244,000,000	$82,350,000	$11,650,000
4000	1500	$30,000,000	$244,000,000	$91,500,000	$122,500,000
4000	1500	$75,000,000	$244,000,000	$91,500,000	$77,500,000
4000	1500	$150,000,000	$244,000,000	$91,500,000	$2,500,000
4500	1200	$30,000,000	$274,500,000	$73,200,000	$201,300,000
4500	1200	$75,000,000	$274,500,000	$73,200,000	$126,300,000
4500	1200	$150,000,000	$274,500,000	$73,200,000	$51,300,000
4500	1350	$30,000,000	$274,500,000	$82,350,000	$161,150,000
4500	1350	$75,000,000	$274,500,000	$82,350,000	$116,150,000
4500	1350	$150,000,000	$274,500,000	$82,350,000	$41,150,000
4500	1500	$30,000,000	$274,500,000	$91,500,000	$152,000,000
4500	1500	$75,000,000	$274,500,000	$91,500,000	$107,000,000
4500	1500	$150,000,000	$274,500,000	$91,500,000	$22,000,000
5000	1200	$30,000,000	$305,000,000	$73,200,000	$201,800,000
5000	1200	$75,000,000	$305,000,000	$73,200,000	$156,800,000
5000	1200	$150,000,000	$305,000,000	$73,200,000	$81,800,000
5000	1350	$30,000,000	$305,000,000	$82,350,000	$192,650,000
5000	1350	$75,000,000	$305,000,000	$82,350,000	$147,650,000
5000	1350	$150,000,000	$305,000,000	$82,350,000	$72,650,000
5000	1500	$30,000,000	$305,000,000	$91,500,000	$188,500,000
5000	1500	$75,000,000	$305,000,000	$91,500,000	$143,500,000
5000	1500	$150,000,000	$305,000,000	$91,500,000	$58,500,000

This table allows you to quickly see how different combinations of assumptions affect the project's economics.
*gpt4o