You can work it out from the plan limits. At the Team limit, $249 divided by 400 chat interviews is about 62 cents per interview. On annual billing, $124.50 divided by 400 is about 31 cents per interview. At the Starter limit, $99 divided by 100 chat interviews is 99 cents per interview, or about 50 cents on annual billing.
Voice is counted in minutes. At the Team limit, $249 divided by 300 voice minutes is about 83 cents per minute, so a 15 minute voice interview comes to about $12.45 when you use the whole plan on voice. Chat and voice share the same plan price, so you decide how to split the month. The ai moderated interviews page explains when each format fits.