Doc, yes, you can build up a bike yourself for less if you already have the knowledge to pick out compatible the components, including cables, ferrules, and barrel adjusters (if necessary), you already own the tools, and you have the skills to install and adjust everything youself. Most people don't own a headset press; therefore you have to factor in the cost of having your LBS install the headset. Buying all your parts off eBay takes a ton of knowledge because you can't truly comparison shop to make a decision and you also have to be able to spot the mismarked items. I've caught more than one. Part of the additional cost of parts from an LBS is to pay for their knowledge when you don't have it.

Yes, it can be done. My husband and I do build bikes this way exclusively. But the type of question allabouteva posed indicated to me she probably doesn't have the knowledge at this point in time to do this let alone the motivation. Some people don't find the huge amount of effort it takes to build a bike this way at all fun. They'd rather be out riding. The effort is too costly.