Is wheelbuilding worth it in terms of trying to save money or building something custom when buying parts from China?
Short answer, NO. Long answer, YES
Short answer: If you purchase the minimum tools required to build "one pair" of wheels, and count all of the time (time = $) you spend properly building the wheels, you will find that it costs you more overall than purchasing prebuilt.
Long answer:
1. If you enjoy projects and learning how to assembly/build things and overall enjoy things mechanical, then YES.
2. I usually save between $50 and $150 per wheel I build, and the wheels are to the specifications I decide I want. (This takes a fair amount of time to research the hubs you want to use - components weights, component durability, # spoke holes, lace pattern, types of spokes, nipples you require, rims...
3. You have to build enough wheels to pay off your investment in the tools required to build wheels.
4. Don't fool yourself into believing that you can start building a lot of "custom" wheels and make extra money. There is a lot of global competition out there, and the economics really don't work that well. But when you become proficient, you can build wheels for friends/family and help them save money.
4. Don't think you can sell some of you wheels right away. be 100% sure you wheel builds hold up before considering letting others use your wheels. (Liability concerns. If a friend's wheel you build fails, it could come back to haunt you.)