6.8 ammo is definitely more expensive than 5.56/223 ammo. Looking for and waiting for a good sale and then buying plenty helps some. Having a 5.56 upper for the same lower helps keep practice and plinking costs down too, one reason I went with a standard AR15 set up rather than the LWRC dedicated 6.8 set up.
If you already have a 5.56/223 AR then a 6.8 upper and a few magazines sets you up. (Since you may not know, I'll mention that the 6.8 required a different bolt than the 5.56/223. Same BC just a different bolt. And along those lines I will mention that the Magpul 6.8 magazines work ONLY in LWRC lowers. I use ASC 6.8 magazines and have had no issues with the six I own.)
JPK
If you already have a 5.56/223 AR then a 6.8 upper and a few magazines sets you up. (Since you may not know, I'll mention that the 6.8 required a different bolt than the 5.56/223. Same BC just a different bolt. And along those lines I will mention that the Magpul 6.8 magazines work ONLY in LWRC lowers. I use ASC 6.8 magazines and have had no issues with the six I own.)
JPK