When Researching A New Product Idea - What Is The Minimum Amount Of Searches I ?

When Researching A New Product Idea Seeking a Affiliate Product To Promote - What Is The Minimum Amount Of Searches I SHould be Looking For To Make It Worth My While To Pursue ?

Out of the following which are right or wrong ?

1) 1k - 3k for high priced or low priced

2) 3k - 5k for high or low priced

3) 5k - 10k up for either high or low priced products

What is the rule of thumb on this that we should always go by when in the process of selection of determining if there is enough interest what is the minimum amount we should accept for high or low priced products ?