Be careful of your jurisdiction. In some places, the act itself of secret recording can be a criminal offence. In that case, you will want to include the possibility of prison in your cost-benefit analysis.

E.g., Germany: StGB 201 § 201 Verletzung der Vertraulichkeit des Wortes https://www.gesetze-im-internet.de/stgb/__201.html

In some places, secret recordings are useless as evidence (e.g., two-party consent states in the United States), while in others even illegal recordings may be admissible anyway (e.g., Sweden).