Annoying cashier at Office Depot

So, on Tuesday, after I got off work, I drove down to Office Depot because it's only a block away from work. I went to go see if they carried the disposable fountain pens that I told Daniel about. They did. But they didn't have any out. To not waste my trip, I walked around and around. And I ran into Jack and Sol. Funny. I ran into them last week at Wal-Mart, too. Anyway, I ended up finding a all-in-one printer that was on sale. My printer hasn't been working for over a month and I've been wanting to print stuff out. Since this one was on sale, I decided to go for it. My wallet may be hurting later (it was on sale for 39.99). I get to the cashier to pay and pick up the printer. The lady tells me that I will need a USB cord for my printer. I told her I had one at home. She said, the one I have at home might not be the same one. She gets a cord for me. I look at it. I tell her I think it's the same one I have at home. She tells me to buy the cord because I will need it. I tell her no I have one at home and that I don't need it. She says I do. We go back and forth and I get tired of this because there is a line behind me. She tells me to buy it and if I don't need it I can return it. Because she says I don't want to get home and find out that I do need it. Well? Guess what? I WAS RIGHT. Someone needs to tell her that the CUSTOMER is always RIGHT. Okay, well... being a sales associate, I know that isn't true. But I was right. I told her that I didn't need it and I did go back to return it that same day. Funny thing was, the lot was emptier when I was there around one. When I went back around five, the lot was fuller. But when I was there at one, there was two or three cashiers and an emptier lot. When I came back and the lot was more full, there was only ONE cashier. Makes a lot of sense? Huh?