ISA gave way to PCI, PCI gave way to AGP, and now AGP is giving way to PCI Express. When a technology first hits the market it is generally more expensive to cover the development costs. Once it is established the costs come down. The silicon and plastic cost the same whatever the technology so eventually PCI and AGP will be obsolete and PCI Express will be the standard until the next development. The only real advantage to staying with PCI and AGP is that there is a lot of cheap slightly old stuff around using the old technology, whereas PCI Express will all be the latest and therefore most expensive. I could build a computer using PCI and AGP for under £300 including the monitor. I doubt that I could do that with a PCI Express system.