No. Forwarding is included in the $99/mo plan. If you eventually own the number and move it to your own carrier, per-minute rates depend on whoever you pick, but they’re cents per minute. That’s less than $2/hour.
If you’re paying someone $10/hour to answer the phone, the call itself costs about a tenth of what the person answering it costs. The cost of generating the call (advertising) is much higher than either. Phone calls just don’t cost much any more and rarely matter the way people sometimes think they might.