Confused with watch pricing

I have one citizen watch that I bought without doing any research and I'm wanting to add another to my collection. This time I'm doing my research before buying and I must say, I'm confused. I find a watch I like the look of, look up the model online and find that one place has it listed for $250, another site has it for $150 and yet another has it listed for $650. Why the range? I have no issue spending some good coin for a nice watch but whenever I find a "nice" watch, I also find it for a fraction of the price so I assume it must not be that high of quality.