Can We Afford The Perfect Prompt? Balancing Cost and Accuracy with the Economical Prompting Index

Tyler McDonald, Anthony Colosimo, Yifeng Li, Ali Emami


Abstract
As prompt engineering research rapidly evolves, evaluations beyond accuracy are crucial for developing cost-effective techniques. We present the Economical Prompting Index (EPI), a novel metric that combines accuracy scores with token consumption, adjusted by a user-specified cost concern level to reflect different resource constraints. Our study examines 6 advanced prompting techniques, including Chain-of-Thought, Self-Consistency, and Tree of Thoughts, across 10 widely-used language models and 4 diverse datasets. We demonstrate that approaches such as Self-Consistency often provide statistically insignificant gains while becoming cost-prohibitive. For example, on high-performing models like Claude 3.5 Sonnet, the EPI of simpler techniques like Chain-of-Thought (0.72) surpasses more complex methods like Self-Consistency (0.64) at slight cost concern levels. Our findings suggest a reevaluation of complex prompting strategies in resource-constrained scenarios, potentially reshaping future research priorities and improving cost-effectiveness for end-users.
Anthology ID:
2025.coling-main.471
Volume:
Proceedings of the 31st International Conference on Computational Linguistics
Month:
January
Year:
2025
Address:
Abu Dhabi, UAE
Editors:
Owen Rambow, Leo Wanner, Marianna Apidianaki, Hend Al-Khalifa, Barbara Di Eugenio, Steven Schockaert
Venue:
COLING
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
7075–7086
Language:
URL:
https://aclanthology.org/2025.coling-main.471/
DOI:
Bibkey:
Cite (ACL):
Tyler McDonald, Anthony Colosimo, Yifeng Li, and Ali Emami. 2025. Can We Afford The Perfect Prompt? Balancing Cost and Accuracy with the Economical Prompting Index. In Proceedings of the 31st International Conference on Computational Linguistics, pages 7075–7086, Abu Dhabi, UAE. Association for Computational Linguistics.
Cite (Informal):
Can We Afford The Perfect Prompt? Balancing Cost and Accuracy with the Economical Prompting Index (McDonald et al., COLING 2025)
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PDF:
https://aclanthology.org/2025.coling-main.471.pdf