I've actually priced it out and there is still a lot of benefit in doing this way. It still comes out cheaper than equivalently spec'd pre-builts and obviously comes with its benefits ("factory" overclocking, choice of case, better power supply/general build quality, etc). My 10%ish build fee + shipping/moneypak fee is a lot less than the markup companies do on the components on pre-builts + shipping + tax. I'm not charging a whole lot for it because its something I enjoy, because of that no online site/pre-built can really compete with my prices. If I were to charge a 40-60% markup like most online retailers, then obviously the value for the customer would be diminished.