OpenAI 全面实行预付费了，最低5刀充值，1年有效期，不可退款。

https://help.openai.com/en/articles/8264644-what-is-prepaid-billing
OpenAI Help Center
Setting up and managing prepaid API billing | OpenAI Help Center
Purchase API credits, manage automatic recharges, and understand credit expiration, payment failures, and balance limits.