Show HN: I built a free API cost calculator after a $340 surprise invoice (apicalculators.com)

A developer has launched a free API cost calculator designed to help users estimate their monthly expenses when using large language models (LLMs) like OpenAI's GPT-5.5 and GPT-5.4 nano, Claude Sonnet 4.6, and Google's Gemini 3.5 Flash. This tool allows developers and product teams to input variables such as input and output tokens per request, alongside their expected monthly request volume, to calculate total costs based on June 2026 public API rates. These rates highlight significant differences in pricing; for instance, GPT-5.5 charges $5.00 per million input tokens and an astounding $30 for output tokens, making it crucial for organizations to budget accurately to avoid unexpected charges. This calculator is particularly significant for the AI/ML community as it empowers developers to better manage and predict their API expenses, a concern that resonates widely following incidents of unexpected billing. By comparing costs across various models, users can select the most cost-effective solutions for their projects, with alternatives like GPT-5.4 nano becoming particularly attractive for budget-conscious applications. Beyond mere cost estimation, the tool also outlines strategies to optimize spending, such as prompt caching and switching to lower-cost models, reinforcing the importance of budgeting and efficiency in today's AI-driven landscape.