We have a IBM xseries server , which has the bay for the hard drives. It came with 2 hot swap drives.  

 Now one of the drive went bad and i need to replace it with another one, when I checked the drives its costing around ( $300).

 The look like regular  SCSI drives with some frames around.

  Can i buy the regular SCSI drives and the frame around to save some bucks ??

 

Most of the x-series servers use what is called a converged tray drive.  That means the drive and tray are combined and not meant to be changed.  If you look at the tray around the drive see if it has special hex type screws?  if so you have a converged tray drive and no, you are not suppose to change just the drive that is why they have the special screws.  People do changed then but it could cause problems.  If you just have the black tray that has standard screws those are meant to be changed.

Depends on what you mean by 'Regular'.  SCSI drives come in two mechanical flavors...  68 Pin for non hot swap applications and 80 pin for hot swap applications.  68 pin drives have a separate power plug while the 80 pin merges the power into the SCSI connector.  They are not directly interchangable.  You can get an adapter to allow use of 80 pin in a 68 pin cabled environment but you cant use a 68 in an 80 pin environment.  

You can change the drive in the tray if you have an 80 pin drive (if you can get the magic screwdriver)  but it could lead to issues.  IBM uses specific firmware in its drives and doesnt test generic drives.  ServeRAID Manager will also complain about the non-IBM drive.  IBM doesnt want you to change the drives in the tray because they are quite susceptable to handling damage and the more you handle them the more likely you are to break them.