As previously mentioned, drilling out the baffles is a mod that can be done pretty much for free if you have the right drillbits. Just make sure you don't drill too big or it'll lean out and pop. Also, holes in the airbox seems to be a cheap mod. I'd be very hesitant to do both at the same time until I had a fuel controller just in case it leans out too much from the combination.
For looks, getting rid of the stickers and reflectors is free and was one of my first mods. If you can spend a little money on paint, a lot of people will agree that painting the side covers does a LOT for cleaning up the look. I have pics of mine in another thread around here somewhere. Do a search for painted side covers and you'll find it. Note: I have a blue fury which requires a base coat. Total cost for all of the paint I needed was around $100. It'll be less if you have a color that doesn't require the base. Here is a link to the site:
Paint Search :: Color Results - ColorRite Leftover paint can be used for things like home made side mount license plate brackets and accenting future mods...
As far as cost of mods goes, my theory is that the aftermarket companies know that there isn't a whole lot of competition out there right now and they can pretty much get away with charging whatever they want... I know quality costs money... But cost does decrease with added competition. It's simple supply and demand. Look at the prices of ammunition at a sporting goods store right now...
Hope I've helped. Good luck and keep us updated.