> if my loans are $50k, and I or my lawyer think that the odds of getting them eliminated are <1%, then based on the expected value, I should spend less than $500 of time and effort on it.

Leaving the probability aside, this assumes that expected values of money are linear. The negative value of debt grows faster than linear; a debt of $50000 is not exactly 10 times worse than a debt of $5000, if you can arrange your finances to pay the $5000 but could never successfully pay $50000 (for instance if the amount you can afford to pay down regularly would cover a large part of the principle on the former but almost entirely interest on the latter).