Vapi, Retell, and Bland AI promise rapid voice AI deployment. Custom solutions promise flexibility and cost savings at scale. The right choice depends on your volume, budget, and requirements. Through deploying both platform-based and custom voice AI systems, we've calculated exact break-even points where custom becomes more economical.
Voice AI platform comparison: managed services vs custom solutions
Cost Analysis at Scale
| Monthly Volume | Vapi Cost | Retell Cost | Custom Cost |
|---|---|---|---|
| 10K minutes | $1,500 | $1,800 | $1,000 |
| 100K minutes | $12,000 | $14,000 | $5,500 |
| 500K minutes | $55,000 | $65,000 | $20,000 |
Break-Even Analysis: When Custom Becomes Cheaper
50K Minutes Monthly (Low Volume): Platform cost: $5,000-6,000/mo (Vapi/Retell pricing). Custom system: $40K-60K initial development + $1,000-1,500/mo infrastructure = $4,300-6,500 monthly year one. Verdict: Platforms win—custom payback takes 8-12 months. Not worth complexity at this scale.
150K Minutes Monthly (Medium Volume): Platform cost: $15,000-18,000/mo. Custom system: $50K-75K development + $2,500-3,500/mo infrastructure = $6,700-9,750 monthly year one. Custom breaks even month 4-6. After payback, save $12K-15K monthly. Annual savings year 2+: $144K-180K. Custom becomes compelling.
500K Minutes Monthly (High Volume): Platform cost: $50,000-60,000/mo. Custom system: $75K-120K development + $6,000-8,000/mo infrastructure = $12,250-18,000 monthly year one. Custom breaks even month 2-3. Annual savings year 2+: $504K-624K. Custom is mandatory at this scale—platforms become prohibitively expensive.
Cost comparison showing break-even points between platforms and custom solutions
Technical Capabilities Comparison
Latency & Performance
Platform Latency (Vapi/Retell): 800-1,200ms typical response times due to multiple API hops—your server → platform → LLM → TTS → platform → your server. Additional overhead from platform abstraction layers. For most applications acceptable, but noticeable pauses in fast-paced conversations.
Custom Solution Latency: 400-700ms through direct integrations and optimized pipelines. Your server → LLM API (parallel) → TTS API → customer. Parallel processing of AI inference and TTS generation cuts latency 30-40%. Our Altorch platform achieves sub-600ms consistently through architectural optimization platforms can't match.
Integration Flexibility
Platform Limitations: Pre-built integrations for common tools (CRMs, calendars). Custom integrations possible but constrained by platform webhooks and API structure. Complex workflows requiring multi-step logic or conditional branching hit platform limitations quickly. Voice quality and TTS providers locked to platform choices.
Custom Advantages: Direct control over entire stack enables any integration imaginable. Multi-CRM workflows, complex conditional logic, proprietary internal systems—all straightforward with custom code. Switch TTS providers instantly (ElevenLabs → CartesiaAI → PlayHT) without platform migration. This flexibility becomes critical as requirements evolve.
Decision Framework
Start with Vapi/Retell if: You're testing voice AI viability (under 50K min/mo), need deployment within days not months, have limited technical team, or are validating product-market fit. Platforms excel at MVP and proof-of-concept where speed matters more than cost optimization. Their managed infrastructure handles scaling, monitoring, and updates automatically.
Build custom if: You're scaling beyond 100K min/mo, need specific integrations platform doesn't support, require sub-800ms latency for user experience, want to avoid platform lock-in and pricing risk, or need fine-grained control over voice quality and processing. Our custom systems deliver better performance at 50-70% lower cost once initial development is amortized.
Get Expert Voice AI Guidance
Zaltech AI deploys both platform-based and custom voice AI systems. We'll help you choose the right approach for your volume and requirements. Schedule a consultation.