What does voice AI actually cost you when it underperforms in production

I've been in this industry long enough to know that vendor demos are basically theater. Every platform sounds flawless when the sales rep is at the wheel. But I've been burned enough times that I now have a list of questions I run through before I'll even consider signing anything. Our call center handles inbound support for a mid-market SaaS product. About 600 to 800 calls a day, a mix of billing questions, basic troubleshooting, and the occasional genuinely complicated issue that needs a human. We've tried two different voice AI solutions over the past 18 months. The first one was a disaster in ways that weren't obvious until month three, specifically around how it handled callers who didn't follow the expected flow. The second was better but had latency issues that drove complaints through the roof. So before I go down this road again I want to hear from people with real production experience, not sandbox testing. What does it actually cost you when voice AI gets it wrong? Not in theory, but in practice. Lost calls, escalations that shouldn't have happened, agents cleaning up after bad handoffs. I want the honest version, not the version in the case study PDF.