you won't save any money doing it yourself.
But it's not always about the money. If you want your AR built with certain accessories, then you may have to build it yourself. It depends on what you want.
Would it be better to pay a little more for an AR that comes with a front flip sight and free float keymod handguard and picatanny rails or buy a AR with standard handguard and A2 fixed sight and replacing them with aftermarket pieces myself?
AR-15's: Barbie Dolls for men.
Seriously, you probably need to look at cost and your skill level. If you're not skilled at building guns and paying attention to what your changing and how that affects the operation of the gun, then buy ready to shoot.
I don't build AR's to save money, I build them to get exactly what I want.