There are many guitar shows around the country, and serve as a good place to get your name out to retailers and people who might not otherwise have a chance to see your work. You can also contact bass only retailers, ebay, craigs list, etc. Anywhere you can put one of your basses, will get some notice, and it's really worth having them in some type of public eye.
As for keeping costs down, like Tribal said, buying bulk is mandatory. talk to the companies you like to use, and sometimes they will make you deals on quantity. I buy Tuners in bulk, 20 - 30 sets at a time, and usually pay about $22 to $26 for a set of four. I also have pick-ups wound for me by a local winder. This is also a big savings. Woods are a little harder, unless you have dealt with sellers directly. A lot of sellers that have really nice figured stuff, 3A to 5A stuff charge obnoxious prices for it. Look to local hardwood sellers, develop a repoire with them, and you will find you get the better pieces for reasonable prices as you become more regular. Try to avoid the overpriced sellers, unless they have something you REALLY need. Otherwise it's not justifyable to spend $300 for a top set you can find somewhere else for $100. You just have to do your research when it comes to woods. Good Luck.
Also.....buy rough sawn whenever possible, if you have a planer or surface sander....another big savings.