Real missed calls per month = calls per week × 4.33 weeks × share that isn't spam × share that go unanswered. Monthly cost = real missed calls × your average call value.
Time lost to spam = spam calls someone answers × minutes each. By default the calculator assumes 85% of calls are spam and each one you pick up costs 3 minutes; change either to match your line. The point isn't the exact number. It's how few saved calls it takes to cover $29 a month.
Callers with a real need rarely leave a voicemail. They call the next name on the list, and you never find out what the call was worth. Fast Response answers on your own business line, books the job or showing, and texts you a summary, and your team can still pick up any call live.