From Fallen London Wiki

ok. i've done the math. every Infiltrator of the Tracklayer City cashout i know of so far results in approximately twice the efficiency of any other simple grind for the resulting resource, if one entirely neglects the price of building infrastructure back up and waning back down.

that's a really large margin for those amortizable costs to cut into. god fucking dammit, i think this might actually legitimately be optimal. :<