I think it's generally a wise idea to quote prices of those exchanges that allow everyone to easily get their money in and out, not just some people 
No such thing. If there was, the prices wouldn't be skewed like this. Also, see below.
Ah, so some people get to enjoy that arb. Nice way to do business. Almost like the traditional money industry.
You can thank the traditional money industry. Do you really think that gox decided to cut off 75% of their customers?
Once upon a time, there were a variety of ways to get money in and out of gox, and pretty much everyone could do it. Over time, almost all of those ways closed up, leaving only wire transfers between Japanese banks. This happened to every exchange, forcing most of them out of business.
Now, we have a variety of exchanges, but for the most part, each of them is only able to serve a relatively small portion of the world because the traditional banking industry in their country will only allow them to interact with locals.