Well, the only reason I got mine was because it was $430 but after my employee discount, store credit and a gift card I only ended up paying $130 out of pocket. But after playing my PS3 a bit, I would have gladly put down the original used price.
The most likely reason it's refurbished is because there was some problems with the first couple of batches of PS3s, primarily 60gbs. But after they've been refurbished, they worked perfectly.
Another reason it could be refurbished is that it's just a used system that it's original owner didn't appreciate as much. At Gamestop, it's policy that whenever we get a traded in PS3, we have to ship it off to our warehouse as defective even if it's not, just so it can have its memory cleared, same with PSP Memory cards and 360 Hard drives.
So it could be a defective system that was fixed, or simply a used system with its memory cleared. I'd say go for it.