Text pricing has two sides
Input includes system instructions, conversation history, retrieved context, tool schemas, and user content. Output includes visible text and, depending on the model contract, billed reasoning or tool-call tokens. Generation-heavy workloads are sensitive to output rates; RAG can be dominated by input.
Estimate with observed percentiles rather than one average prompt. Long-tail contexts can dominate the bill.
Media uses different units
Images may vary by model, count, resolution, quality, and editing inputs. Video commonly depends on duration, resolution, frames, or model tier. Audio can depend on characters, tokens, or seconds. Read the unit next to the rate before comparing providers.
Async job retries and abandoned results still matter if generation completed.
Price per unit is not cost per outcome
Add retries, malformed output, human correction, verification, and orchestration steps. For agents, sum the whole trajectory. For media, include the number of variants needed to produce one usable asset.
The winning model is the one with acceptable quality and the lowest cost per successful task, not necessarily the lowest rate card.
Build a living forecast
Track volume, input and output distributions, model mix, cache effects, retry and fallback rate, media settings, and growth. Recalculate when models, prompts, retrieval, or product behavior changes.
Keep assumptions beside the result so finance and engineering can challenge the same model.
