Present day PCs (and Macs) can be amazingly powerful and relatively inexpensive.
I have emphasized the word relatively because you should not expect computer vendors not to be after money in your pocket. And so, they keep prices of their PCs always at the higher rather than lower side by a variety of means, which include closing down older model lines and rolling out machines with faster CPUs, more memory, more disk space, and larger displays, whether you, dear user, need it or not. They have to keep their prices sufficiently low to lure you into their shops, but not so high that you would find their equipment unaffordable. There is some competition in this business that helps keep prices down, but not enough. Nowadays we are down to two major US PC vendors, Dell and HP, with Gateway, IBM and Apple mopping up crumbs that fall off the table, two Japanese vendors that count, Toshiba and Sony, and Taiwanese Acer.
Compare this to the glorious world of automobiles, where you have three major US vendors, six Japanese vendors, three Koreans, three great German companies, three French, two Swedish, four Italian and a plethora of British exotica. Even though some of these have been bought by others, their distinct production lines survive and compete offering a great variety of products to people around the world.
But let's get back to computers. Whatever competition there still is in this business, is enough to keep pushing computer performance up and their prices down enough to provide us with laptops with 3 GHz CPUs. I saw some people write that their laptops had as much computing power today as supercomputers had only ten years ago. Such statements make great advertising lines, but they are quite incorrect. They are incorrect, because it is only the CPUs themselves that have computational power matching that of ten years old supercomputers. Other PC components, like memory, system bus, IO interfaces, etc., lag well behind those of even ten years old supercomputers, and so these laptops, although quite useful, are not really in the supercomputer league. But they can perform certain operations very quickly, especially the ones for which they are highly optimized: fast screen redraw, fast searches on cached data, fast handling of interrupts - the stuff that is important to PC users.