This is very eloquent but somewhat verbose and rambling in parts. The only solid take aways i pulled from it are:

1. The assumption that if its easy than any one would have done it in some markets is very true but is not a universal maxim.

2. You have to search out the markets where that is less true.

To expand on the station analogy with the $20 bill they mention in the middle of the station where the traffic is highest but what about in the alley behind the station or next to the stand with the new careless employee? Arbitrage isnt just limited to the most trodden popular paths (s&p 500). The context always changes the ebb and flow surrounding arbitrage, whereas you cant fight the raging river and expect to beat it, you may find opportunity in a swirling eddie