How I Cut My AI API Costs by 70% (With Real Invoice Numbers)

─── I've been building an AI-powered IELTS speaking practice app. The core pipeline is straightforward: Whisper for speech-to-text → GPT-4o for evaluation and feedback → TTS for audio response. Before launch, I ran the numbers and nearly killed the project on the spot. At 100 daily active users doing 3 sessions each, API costs alone would eat ¥3,000+/month (~$420). No revenue yet. Just burning cash. Then I found SubRouter. Here's what happened after a few months of real usage. The Actual Numbers No cherry-picking. These are my real account stats: Metric Value Total spent (SubRouter) ¥3,538.78 (~$490) Total API requests 6,447 Total tokens consumed 7.15 million+ Equivalent cost at official pricing ¥8,000–¥15,000 ($1,100–$2,070) Savings ¥4,461–¥11,461 (~56–76%) What Is SubRouter? SubRouter is an API gateway that proxies requests to major AI models — OpenAI, Anthropic, Google — at 60–75% below official pricing. The interface is 100% OpenAI-compatible, so any SDK that supports a custom base