Does a high ablation score for a reranker prove it is the best area for investment?

It is critical to distinguish between the integral (total contribution) and the derivative (marginal return). While removing the reranker entirely might cause a significant drop in performance, proving it is an essential component, this does not mean that further investment in the reranker is more valuable than adding more documents. To make an informed decision, one should score queries with a stronger reranker while keeping the number of documents constant to see if the marginal improvement justifies the cost.