The first one. All of the other examples are talking about things price-wise, whereas a cheap excuse is a very bad excuse.
I think you should use for example, because that second sentence is an example of the first. Hope this helps.
Answer: He is referring to his discovery that the secret to a creative writing for him was using a method of word-association to write fiction.
Explanation: He would get up every morning and write down at his desk any string of words that would come to him. Then he would begin to develop a story from it.
He would take walks along familiar places and go down memory lane writing on acquintances and loved ones he once knew or that had passed on.
