Depending on what you want, Computers are still expensive today, I just looked on Dell.co.uk and tried to place the Specs of My computer, it didn't go as high as mine is Graphics Memory, Added Cards, Ect, But it was still telling me it would be at least £900, For a system less powerful than mine which only cost about £400, (including Moniter, printer, Ect), Although i guess it depends on what you want from a PC and where you get it from, I recently built one for a friend for only £100, Even got a 17Inch Monitor for only £7.50, (about $15), 2nd hand, but in good condition
But personally I've never brought a prebuilt PC from a Store, I got my First PC from a Company that was throwing some away, cost me nothing, and even got a nice server case which is still in the loft somewhere.
Everyone Be Cool, You, Be Cool.