With the OEM/Bulk NEC-2500A, you get the drive only. No cable, manuals, CDs; just the drive itself.
This is often the case, but there are sometimes add-ons to sweeten the deal for a small increase in price. It depends on the dealer.
When I bought my OEM/bulk NEC ND-2500 at NewEgg a few days ago, there was an option to bundle it with a OEM version of Easy CD/DVD Creator 6 Basic for $8 more. And there was also a free gift of five NewEgg/Ritek GO4/L19 -R discs thrown in! So, except for a printed quick start manual and perhaps an IDE or audio cable, this OEM package was getting close to what a retail package could have been.
Since this was to replace an existing drive in my system, I had no need for the cables. But for the person needing cables and mounting screws, etc., a retail package version might be more cost effective than OEM...