A lot of people make the argument "start with a performance car FIRST!"
I think the reason people are modding econoboxes is because they don't have enough money for a Mustang. Now here comes the $/HP ratio, but there's one thing that most people don't take into account: insurance. For a young person, insuring an econobox is A LOT cheaper than insuring a performance car. I pay almost $200 bucks a month for my Intrepid as it is (it's actually for two cars, it would double if i just had the Intrepid on it). Can you imagine if I'd have gotten a Mustang?
Now, I'm not condoning stupid ricer accesories that don't really do any good. I'm just saying think about it:
A young kid needs a cheap, first car that isn't an arm and a leg to maintain and insure. He/she takes on the performance hobby and makes his Civic/DSM/Whatever as fast as a stock Mustang. Well, he has a reasonably fast car that is his cheap, affordable daily driver. No, it won't take on a modded sports car, but as long as you don't think it can, then that's cool.
I just don't agree with bashing a guy that truly puts meaningful mods on his car.