In general, it is cheaper to buy a basic bicycle instead of building it. Basic bicycles are affordable hybrids and road bikes that you can find for around $500 and $1,000.
Building a bicycle requires a lot of parts and even more expertise. An experienced bicycle mechanic may be able to build a bike for cheaper than if they were to buy it.
Wheelbuilding and bike building are great for experienced bicycle mechanics who enjoy the building process. They might even be able to build a bike for cheaper than buying one.