pistol purchase question

went to a local store today to look at what there price would be on an M&P 9mm. The instore price was $519. On their website they were listed for $452. I asked why the difference and she said that was the website price. She said that I could order it from the website and it would be at the store in 2 days. I don't understand what would make a store owner do it like this. She told me that the markup is like 2% at $452. Of course I jumped all over this.