Well I'm not defending anyone on either side of the losing 600 dollars in fish. But I have made some major mistakes in my short time in this hobby.
The mistakes that I did make cost me most of my fish, like 80%, each time I made a mistake. Now saying that, I have had no more than 6 fish in my tank at a time. I did learn from the mistakes after the fact. My big problem is that I didn't do enough research before i started and then after my 1st mistake. I have learned from all mistakes.
I am more cautious about buying fish and what I put in my tank. I also keep a relative close eye on my parameters.
I can see where someone has lost 600 dollars, some of these fish are expensive especialy if a LFS marks up their prices a little too much. My LFS is very reasonable because I've been dealing with them for 5 years.
But on the other hand, you need to do research and need to limit your losses. I guess I can agree with both sides to a point.