It reads to me that:
1) The auction claimed a New In Box Mac w/ 7200rpm drive
2) The item that arrived contained said 7200rpm drive, but the actual computer box itself had specs printed on it that stated the computer came with a 5400 rpm drive.
3) The screen cleaning cloth was missing.
So it seems that the OP is concerned that the laptop was really not New In Box because it appears that the hard drive, although specified as a 7200 in the auction (and what is in the system) was not the original drive from the manufacturer implying that the system is not really "new in box".
To the OP: There are several of possibilities.
It's possible he bought it at a store, bought a hard drive upgrade which was installed at the store, then later decided he didn't want it (as an example, I have a Mac Mini that I bought new, it came with 2 gig RAM, I had it upgraded at the store to 4 Gig (I didn't want to crack the case as getting into a mini is a pain) - technically since it was upgraded by the store one could argue it's still NIB since I hadn't opened it yet, but really since the box was opened, it's probably best to consider it LNIB).
It's possible he bought it, bought a bigger/better hard drive and installed it himself (really not a difficult task on current gen Macbook/Macbook Pro (not like a powerbook where you had to dig into it to get to the hard drive))
Either way, there aren't too many 500 GB 7200rpm laptop drives on the market, and from what it sounds, you got a seagate drive, which is - from reviews - a good drive.
You can always ask the seller why there was a discrepancy between what is printed on the box vs what was in the box - but it's not like there was something better that was made lesser, it was something lesser that was made better. At best case scenario - you're overreacting to a situation that isn't a problem. At worst case, the seller has a different interpretation of NIB then most people and should have listed it as LNIB (Like New In Box). Not knowing what you paid for it, I can only assume, either way, you probably got a decent deal otherwise you probably wouldn't have placed a bid on it?