Well, first off, how can you tell the graphics are awsome? Most consoles are strictly designed for the capabilities of a TV, which ain't great. Second, they're entirely dedicated systems, which means they can push more power into the graphics without worrying about all the other things the GPU has to do in a PC environment.
Consoles (while I haven't personally owned one since NES) are very popular among gaming companies because they are INCREDIBLY easy to develope for. The hardware doesn't change. Everyone's got the same stuff. That's not the case in the PC world. Also, consoles are cheap because they're mostly made of integrated parts, aren't meant for hardware exchanging, and are typically made from the cheapest parts possible.