Mac spec'ed memory from Non-Apple sources is as cheap as ordinary RAM.
Ok build a similar spec'ed MBP then. High Def 17 inch screen, 10 hour long battery life? Remember in SA Core overcharges for Apple Macs too but even with that. You have to compare a high end Vaio to a MBP. Sure you could buy a 17 inch HP laptop at R8K but the display is 1366by728, the build quality is bad and the battery life is under 2h.
YES you do. Different grade CPUs, HDDs, chipsets get sent to different vendors. Apple, Enterprise Dell, HP etc probably have first pick, OEM usually get the lowest batch, and when it comes to SA - we're probably the lowest tier.