In my opinion if you compare apples to apples when looking at building vs buying, you will always come out cheaper building. That is to say, if you wanted to build a rifle to the exact same specs as one you would buy from larue or noveske you will save money building it rather than buying it from them. You will also save money in the long run by building a gun exactly how you want it the first time than buying a box rifle and changing out parts to get it how you want.
To often I see people saying that building is much more costly than buying a stock rifle from rra or spikes, but they are comparing their super spec build with magpul everything , larue rails, kac or toy buis and whatever else to a bare bones m4. It's just not a fair comparison that way.
For example the noveske crusader rifle costs 2255 from them, my build cost like 1500. It's not the exact same parts but in my opinion just as good if not better. Crusader barrel, battle comp, dd bolt group, larue 10 rail, kac micro buis, bcm gunfighter on the upper, bill Springfield trigger, Ergo grip, Okie stock, u2 buffer, all on mega upper and lowers. 1500 all gotten nib or like nib off the EE here. To me that's saving money on building vs buying.
Pat