I think it's also a little based on the culture of the place where you live. For example here in Italy "tipping" isn't a part of the colture and we don't do it... when we eat in restaurants we pay the "coperto" (usually an euro or two) for the service of the waiters and you can't choose, you have to do it.
If I had to sell something I'd rather put it at a very low price than rely on tipping.
If I had to sell something I'd rather put it at a very low price than rely on tipping.
Thank you for pointing out the cultural differences! Truly, tipping is a cultural factor.
In some cultures they do and in some cultures they don't, what's more look at it as an offense sometimes.
But again, in a system that connects people from very different cultures together, what is this system's culture?
It is undefined and that is why tipping strongly depends on the individual and that is why you cannot base a systematic earning plan on it.
But you are right about the low price selling. If your purpose is making profit, then sell and do not rely on tipping.
Overall, I can sum it up as: tipping is a nice opportunity and far not outdated, but its place is not in a money-making method. Its place is in people's hearts
So it is worth for you as long as you can appreciate it in your project as a favor. 
