Is there a correlation between expensive solutions and big effects?

I think the short answer is not necessarily.
While some expensive solutions may have a big impact, there are also instances where small, low-cost solutions can lead to significant outcomes. The relationship between cost and impact is not always straightforward, and it depends on the specific context and problem being addressed. In some cases, a simple and inexpensive solution may be the most effective, while in other cases, a complex and costly solution may be required to achieve the desired results. Ultimately, the effectiveness of a solution should be evaluated based on its ability to address the problem at hand, rather than its cost.