The Falcon will use standard components. They're basically just building you the same thing you could buy and build yourself, but with lots of nice paint and plastic and stickers on it, plus those little extras. This is good for upgrading later on, but relatively costs more.
Dell uses some proprietary parts, and custom cases. One would think that that would mean higher costs, but their volume is so huge it offsets it, and the parts are cheaper. They also aren't charging you for a "premium" brand name like Falcon, or AlienWare (unless you buy an AlienWare which is now owned by Dell). Dell is known for low price, functional computers that aren't too ugly. The upper end does get to be expensive but is still cheaper than others. However they're also not known as speed-demons, using as much integrated stuff as possible, and some of the cost is subsidized by all the 3rd-party software that gets pre-loaded, and the fact they don't send out operating system CDs with a computer anymore.
Falcon and others like them are now living off their reputations and not much else. They were THE place to go back in the day, if you wanted a high quality, fast as possible system, that also didn't just look like a beige box. Now, they're just selling the same thing you can get everywhere else, using standard parts, and hoping people think the name means something still. Whether the cost is acceptable depends on you, on whether they have a particular case design, logos, or support quality, or even an "exclusive" product. They are good at customization, and you don't get an operating system that's already loaded down with garbage (usually places like that don't install much software), and you get more customization options. But those are still things you could just do yourself.