With the important caveats of 1) the implicit costs of murder-for-hire are probably pretty high (risk of going to jail, e.g.) and 2) killing someone doesn't necessarily make the lawsuit go away—though that doesn't help the person being killed.

So the utility formula is something like:

  (p[c] * c[f] + c[a]) ÷ p[l] > c[l]

  where:
  p[c] = probability of getting caught
  p[l] = probability of the lawsuit being dropped
  c[f] = value of your freedom
  c[a] = cost of an assassin
  c[l] = cost of losing the lawsuit

You can layer in additional probabilities—like the probability of the assassination being successful, or the probability of winning the case. This is just fun to talk about the utility formula of assassinations on HN.

But it's probably true that as c[l] increases, c[f] increases as well, and p[l] drops. So it's rarely (never?) worth this trade-off.