Why I Migrated From GPT-4o to DeepSeek — A Backend Engineer's Notes Six months ago, my monthly OpenAI bill crossed four figures and I finally snapped. Not because the cost was unbearable in absolute terms, but because I had a sneaking suspicion I was overpaying for marginal quality gains. So I did what any sane backend engineer would do: I instrumented my service to log token usage by endpoint, spun up parallel calls to every major Chinese model, and started comparing numbers like my paycheck de