Custom frames seem to start at about $1,500 these days, including the fork, but prices can go much higher.

Are you simply wanting to go custom to get internal routing for cables? Most people go custom because they have unusual fitting needs, or they are splurging because they want a particular color combination or frame features. There's nothing wrong with getting a custom if you are willing and able to pay for it. However, there are so many frame choices available now that a person can usually find a stock bike with the right fit and features.