I'd read about it in the buff books and enthusiast forums, and shook my head. $30,000 for what's essentially a Civic Si with a body kit, rims, shocks, and spoilers? Then I saw one in person. And it did not change my mind one bit. It still looks like a mildly (though tastefully) riced-out Civic Si.
Now, the argument could be made that if you were going to get the equivalent items aftermarket, including wheels, tires, suspension, body, kit and exhaust with the requisite painting, mounting, balancing, installation, etc., that it might add up to about as much -- if not more -- than the approximately $8,000 premium the Mugen fetches over the standard Civic Si, and you couldn't package it in financing at the dealer and have it covered no-questions-asked by your helpful local Honda dealer.
Maybe that's true, but for that amount of coin, I'd expect some substantial improvement in many areas, not least of which under the hood. I could see how you could justify that price if it included the 222-horse Type-R engine offered in Japan and Europe. Never mind the fact that you can buy an unmolested Mazdaspeed3 for around $23k starting, and $27k nicely-loaded that packs a substantial 263 horsepower and 280 lb./ft. of torque. For you math majors out there, that's a little more than double the stock torque output of the Si.
I know the Honda loyalists, the very fact that I'm comparing a Honda to a Mazda is galling, but putting brand loyalties aside, I find the Mugen Si a tough proposition to justify. Certainly, it will have its takers, but for me, the smart money's on the hero from Hiroshima.