To address the high computational cost of LLM-based Text-to-SQL approaches, this paper proposes EllieSQL, a complexity-based routing framework. EllieSQL estimates query complexity and assigns it to the appropriate SQL generation pipeline, processing simple queries efficiently and complex queries computationally intensively. Furthermore, we evaluate cost-effectiveness by introducing the Token Elasticity of Performance (TEP) metric, which measures the effectiveness of performance improvement relative to token investment. Experimental results demonstrate that EllieSQL reduces token usage by over 40% compared to existing approaches while improving TEP by more than twofold without any performance degradation. This contributes to cost-effective Text-to-SQL development and highlights the importance of considering resource efficiency for sustainable Text-to-SQL research.