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 entrance fee:

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

A more modest EPA using up of all the available bonus:

(5 * 12.5 * 1.19 - 120 * 0.01 + 5 * 2.5) / (1 + 20 / 75 * (3 + 15 * 0.2 / 6 ) = 6.76 EPA (for 144 UI)