Modularity is never cheaper? It is when you have competing devices all using the same interface. For example, you never saw cheap microchannel cards (MCA slot) on PS/2 computers because it was proprietary. Same for VMS slots. PLENTY of cheap ISA and PCI cards in the same era, though.

I didn't say it in such an absolute. I said it would make it MORE future proof. I believe that devices with a standardized port or slot will have a LOT more usefulness for a LOT longer than something with an integrated peripheral.