in my experience with pc's one cannot build a cheaper pc than Dell..HP..Acer..etc..etc for web surfing word processing and some very light,and i mean very light gaming.How much are you going to pay for the hp? I can build you a comp for cheaper more than likely..
for an all out gaming beast (like mine) we sure as hell can build a badass system compared to any vendor.
hell a single decent GTX 580 runs near $500,and SLI your looking at a grand..thats just in video cards,but when you build your own..you know exactly what goes into it,and there is no skimpin on things like power supplies like the OEM vendors like to do.