Everyone is still learning. The number one key to succeeding online is testing everything you can possibly imagine. This takes persistence. Money may help as well, but for many large companies this just means wasting tons of money on two million dollar Superbowl ads. Then being nowhere to be seen 6 months later.
Persistence is the key.
An eBook covering fly fishing in Arkansas would be considered a niche market product suitable for a small entrepreneur. The problem with the big screen TV and the toothbrush is that they are available from anywhere. Your prospect would be much more likely to run down to the local Wal-mart and electronics stores than to purchase from you. They don't know who you are. For the Cooking eBook, it is too broad of a subject.