copying headlines but not blog

We usually write about 40 blogs a day and compete with others on the same topic. However my writers and their writers have different styles of creating headlines.

If i were to use different variations of headlines as tags in WP and using a competitor headline as a tag, do they have a case for plagiarism? It wont be exact, but 90% similar to competitor headline..

If that would be the case titles would be as valuable as domains. Whoever had "The 10 Best Blenders" title first could sell the rights for quite some cash.