Smith.ai vs Ruby vs a Custom AI Voice Agent: What a 30-Person Business Pays to Answer Calls in 2026

Short answer: for a 30-person business taking about 600 inbound calls a month at three minutes each, Smith.ai's AI Receptionist costs about $12,000 a year, Ruby's live receptionists cost about $74,500 a year at their published per-minute rate, an in-house receptionist costs $38,010 a year in median pay for business hours only, and a custom AI voice agent costs $15,000 to $50,000 once plus about $2,400 a year in voice platform usage. The deciding number is the per-call gap: Smith.ai's Enterprise rate is $1.67 a call, while a three-minute call on Retell's voice platform costs about $0.33, so a custom agent saves about $1.34 on every call. Below about 500 calls a month that saving is too small to repay a build quickly. All vendor prices below were read from the vendors' own pages on 8 October 2026, in USD.

If you want a range for your own build first, the AI development cost calculator gives one in about a minute.

The routes, with published prices

Ruby's live plans are priced in minutes, Smith.ai's AI plans in calls, and Retell in minutes. The comparison below converts all of them to the same call volume.

What each route costs a 30-person business

Take one business: a home services company or a clinic with 600 inbound calls a month, three minutes each on average, so 1,800 minutes.

Smith.ai AI Receptionist, Enterprise. 600 calls x $1.67 = $1,002 a month, about $12,024 a year, or $36,072 over three years. On Pro the same volume is 600 x $2.00 = $1,200 a month.

Ruby. 1,800 minutes is more than Ruby's largest published plan of 500 minutes. At that plan's rate of $3.45 a minute ($1,725 / 500), 1,800 minutes is about $6,210 a month, or $74,520 a year. Ruby quotes larger plans privately, so treat this as the published-rate ceiling and ask for a quote. What you buy is a human on every call.

An in-house receptionist. The BLS median is $38,010 a year before payroll taxes and benefits. That covers business hours only; evenings, weekends and lunch breaks still need an answering service.

A custom AI voice agent. At Retell's default example of $0.11 a minute, 1,800 minutes is $198 a month, about $2,376 a year. Three-year total: the build ($15,000 to $50,000) plus about $7,128 of usage, so $22,128 to $57,128.

The break-even, worked out

Against Smith.ai Enterprise, each three-minute call costs $1.67 on Smith.ai and about $0.33 on a custom agent, a saving of $1.34 a call.

These are KUMO's calculations on the prices above. Call length moves the answer, because Smith.ai bills per call and Retell bills per minute. A ten-minute call costs about $1.10 on Retell and still $1.67 on Smith.ai, so the saving falls to $0.57 a call and the build takes more than twice as long to pay back. Short, frequent calls favour building; long calls favour Smith.ai's per-call pricing.

When each route is the right one

1. Under about 500 calls a month, buy an AI receptionist. Smith.ai at that volume is about $10,000 a year, and its Enterprise plan includes setup and integrations. No custom build pays back fast enough.
2. If callers expect a human, buy Ruby or hire. Legal intake, high-value sales calls and upset customers are where a live person earns the per-minute price.
3. If the agent must act inside your own systems, build. Booking into a scheduling tool you built, checking job status in your own database, quoting from your own price rules: this is where a packaged receptionist needs custom work anyway, and where owning the logic pays.
4. If volume is high and rising, build. At 1,500 calls a month the gap is about $2,000 a month, and it grows with every call.
5. If call recordings must stay in your own cloud account, build. A custom agent runs where you choose.
6. If nobody will own it after launch, buy. A voice agent needs someone to review calls each week and fix what it gets wrong.

Three quotes for the same brief

Take the brief above and ask three suppliers.

• The packaged route quotes per call: about $1,000 a month on Smith.ai Enterprise, set up for you, live in days.
• A freelancer quotes a voice agent on Retell or a similar platform. Fast to start; the risk is one person, no tests on real recorded calls, and no handover if they move on.
• A senior team quotes $15,000 to $50,000 for a first production version: your number, your booking system, your escalation rules, tests on a few hundred real call recordings, and deployment in your own cloud account.

For a business under 500 calls a month the first is usually right. Above that, or when the agent has to change records in your own systems, the third usually is. Before any route, run the pilot steps in the AI voice agent pilot checklist.

What a Starter Build buys

A KUMO Starter Build ($15,000 to $50,000) is a launched first production version of the voice agent: call handling on your own number, answers from your own policies and price lists, booking or job lookup in one or two of your systems, rules for when it transfers to a person, tests on real recorded calls, and a handover another engineer can continue from. See AI workflow automation for how KUMO scopes it. KUMO's founders built Volopay's first production version as its founding engineers, a finance product where every action had to be traceable, the same discipline an agent that books jobs and takes customer details needs.

Costs after launch

Packaged routes recur monthly: calls or minutes, overage rates, and add-ons such as live agent escalation. A custom agent costs voice platform minutes, phone numbers, hosting and engineering time. On either route, decide before launch who listens to a sample of calls each week; that is the cost most teams forget.

How to get a real number this week

Pull three figures from your phone system: inbound calls per month for the last three months, average call length, and the five most common reasons people call. With the first two you can run the arithmetic above yourself. With the third, a free 30-minute call with an engineer gives a band for your own brief.

FAQ

How much does an AI receptionist cost? Smith.ai's AI Receptionist, read 8 October 2026, is free for 25 calls a month, $150 a month at $2.00 a call on Pro, and $500 a month at $1.67 a call on Enterprise. At 600 calls a month that is about $1,000 a month.

How much does Ruby receptionist cost? Ruby lists $250 a month for 50 minutes, $395 for 100, $720 for 200 and $1,725 for 500 minutes, with larger plans quoted on request. That is $3.45 to $5.00 per receptionist minute.

Is an AI receptionist cheaper than a human receptionist? At 600 three-minute calls a month, Smith.ai's AI Receptionist is about $12,000 a year against a median receptionist salary of $38,010 for business hours only, or about $74,500 a year for Ruby's live receptionists at their published rate.

How much does it cost to build an AI voice agent? A first production version that books into your own systems is $15,000 to $50,000 with a senior team, plus voice platform usage of $0.07 to $0.31 a minute on Retell, about $0.33 for a typical three-minute call.

Can an AI voice agent book appointments into my own software? Yes, if it has access to your booking system's API or database. Packaged receptionists connect to common calendars and CRMs; a custom agent is the route when the system is your own.

Last verified 8 October 2026. Smith.ai prices from smith.ai/ai-receptionist, Ruby prices from ruby.com/plans-and-pricing, Retell prices from retellai.com/pricing, receptionist pay from the BLS Occupational Outlook Handbook, all read on that date in USD. Monthly, yearly and three-year totals, per-call costs and payback periods are KUMO's calculations on those published prices at the volumes stated. KUMO bands are KUMO's published prices.