It probably won't be cheaper unless you have the parts already or are transferring the parts from another bike. However, it does allow you to add the components you want.

I like to tear down, clean and put back together ~30 year old bikes I purchase. This process can take a 4-5 hours and I usually set goals to do certain things in a few days as I loose focus otherwise. Plus, there are certain things that can add time, such as wrapping bar tape, since I try to make it perfect.