Doubting the numbers

> If you have Watchful 167, the best way to build Attar is with Explore the Gatehouse Market in Near Arbor and Walk the walls in Far Arbor. With 100% success, this tends towards 6.02 EPA (54.17 Echoes/trip), but only when done in unreasonably large batches. 

I can’t reproduce the math here. Success at Walk the walls gives 2 Attar, yielding 14 Attar over a 9-action visit to (Far) Arbor. With rare success at Gift your Attar in tribute, I can cash out my Attar hoard at the rate of 12.5E/3 Attar. The limit value should be 14/9 * 12.5/3 ≈ 6.48 EPA. Am I missing something?

Testing the linked simulator with default values for the qualities, I get the following efficiencies:

5.01 EPA for conversion at 100 Attar 5.90 EPA for conversion at 1000 Attar 5.97 EPA for conversion at 10000 Attar 5.55 EPA for conversion at 100000 Attar 4.63 EPA for conversion at 1000000 Attar I can’t see why efficiency would decrease above a certain batch size, so something seems fishy to me here.