Partly because its older and came with Windows 8, I think, but I'm not 100% sure. The whole thing was a little weird. I've been periodically checking Microcenter's website for good deals on one, but wasn't motivated by the listings you saw. But, last Thursday night, I randomly checked and saw this:
Had no idea what the open box note meant, but for the price, I decided to reserve it and go down and take a look at it the next day. Seemed too good to be true, and that's the reason I took the screenshot. When I went down to look at it, I was expecting it to be scratched and dented beyond belief, or have some other glaring defect. But it didn't. It looked brand new.
Something weird had happened with it though - the stickers on the beaten-up box said it was sent from Microcenter back to Microsoft for something to be repaired way back in Feb. 2015, then returned to the Dallas store the next month. What happened to it between March 2015 and last week, I don't know and no one at Microcenter admitted to knowing. But from its appearance, it must have spent a lot of that time sitting on a shelf not getting used.
When we opened the box, it was missing part of the power cable. They grabbed a new one so we could power it on, and then saw that it still had someone's account on it. So, Microcenter re-imaged it. After that, we learned that it was actually an i5 (not an i7 as listed on the website and on the box). That must be what the open box note was about, but why Microcenter ever put it on their website as an i7, I don't know.
How it got into an i7 box, and what exactly happened to it...don't know. But at the end of the day, I walked out of the store with a brand-new-looking Pro 3 for under $400. And it works great. Other than a little trouble getting Windows 8 to update at first, I've had no trouble with it [fingers-crossed].