Welcome to the OpenAI dev community, @Rustemov_Bauyrzhan.
The deep research models are agentic models, which per the Deep Research docs:
The
o3-deep-researchando4-mini-deep-researchmodels can find, analyze, and synthesize hundreds of sources to create a comprehensive report at the level of a research analyst.
Thus, the input costs would correspond to the web search result ingestion and analysis.