> Here’s an interesting graph from the data that proves the price difference increases with price: [followed by a graph of nearly random data]

Drawing a straight line through loosely correlated data doesn't "prove" anything.

> I didn’t do Craigslist arbitrage for long because it was not worth my time and effort.

So a more appropriate title for this post would have been "Failing to bootstrap a startup with Craigslist arbitrage"?