not exactly true.
you can make something look good for pennies if you have the skills to do everything (paint, make parts from scrap, take your time on the details).
you can also make them run good for pennies if you have the ability to tune and re-jet a carb and do all of your own work.
the most expensive part on my bike is the engine itself (which was $85.00 for the whole kit). the rest is just my abilty to make things, pay attention to the details, and do custom paint work. (it also pays to have friends who can do pinstripong and make custom decals for free)
I pick up nice used bike parts for free at the local bicycle recycling shop.
the intial bike show here, complete with the springer frontend cost me $30.00 off craigslist.
new tires were around $30.00, expansion chamber was $50.00 (modified by me), chain tensioner was built from a derailer, seat, sissy bar and handlebars were free, the grips were $5.00, the digital speedometer ( inside a gutted and flipped headlight) was $10.00.
the fenders came on the bike and i chopped them to make them shorter. the rear caliper brake and lever were free, I painted the gas tank and my friend did the pinstriping. another friend made the vinyl chainguard decals for me for free.
exhaust header wrap, left over from when i wrapped the exhaust on my 55 pontiac.
i re-jetted and tuned the carb which cost me around $3.00 for a new jet. better nuts, bolts and washers, approx. $10.00 worth. chopped front spring to lower it, free.
top speed is around 30 mph, but i'm running a 41 tooth sprocket on a 20" wheel which makes it have a lot of bottom end.
I don't have a whole lot of money in it, but i have been offered quite a bit for it.
i have around $300.00 in the whole bike, including the paint, and my bike is definitly a one of a kind and you will probably never see another one that looks just like it.
$300.00 seems to be the average cost for most people to build an average looking "cookie cutter" motorized mountain bike, without a custom paint job.