If all you care about are echoes, you can get quite a bit more out of Extraordinary Implications by upconverting to Uncanny Incunabula and taking advantage of Rat Market markup instead. Assuming Benthic CP is sourced from the Endowment of a University Fellowship, using an assumed epa of 6 to buy Abominable Salts from the Bazaar and ignoring the initial action cost of Rat Market entrance.

Upconverting 25 Extraordinary Implications (valued at 2.5 E each) results in 5 Uncanny Incunabula and an average of 150*0.6=120 Nevercold brass from the luck check (valued at 0.01 E each). The UI value is being multiplied by the maximum Rat Market bonus of 1.32%. Each conversion takes one action and consumes 20 Benthic Cp, which can be accumulated in batches of 75 at the cost of 3 actions and 15 Abominable Salt, which costs 0.2 echoes at the Bazaar. Dividing the salt cost by an assumed EPA of 6 converts the term to an equivalent number of actions.

(5 * 12.5 E * 1.32 + 120 * 0.01 E - 25 * 2.5 E) / (1 action + 20 / 75 * (3 actions + 15 * 0.2 E / 6 EPA )) = 10.97 EPA (for up to 50 UI)

We can calculate an effective Rat Market bonus from maxing out the available bonus echoes by using a weighted average of the two bonuses, which are +32% up to 6500 saturation and +12% between 6500 sat and 18000 sat: (6500 *1.32 + (18000 - 6500)* 1.12) / 18000 = ~1.192

(5* 12.5 E * 1.192 + 120 * 0.01E - 25 * 2.5 E) / (1 action + 20 / 75 * (3 actions + 15 * 0.2 E / 6 EPA )) = 6.87 EPA (for 144 UI)