If you are set on a large frame, ArmaLite is the company to beat for reliability, accuracy, durability of the small parts, and cost.
The cheap parts guns tend to have a lot of problems once you start shooting them, namely in bolt catch pin failures, and overall unreliability. The more you shoot them, the more bugs raise their heads.
If you can afford to plink with .308, then you can afford a good rifle that won’t crap the bed like many on the market do.
Ignore the list price fixed costs and focus on reputation from guys who have been shooting AR-10s for decades and learned the hard way so you don’t have to.
Also budget-in optics, which will likely be more than the rifle if you want quality variable power that won’t break. NF and Vortex Razor line are great easy buttons for durability and quality with great reticle options.
I’ve been shooting, trouble-shooting, repairing, and competing with AR-10s since about 2002. I went back to small frame though in AR-15/Grendel, so I don’t shoot my large frame guns much anymore.
If you can’t afford .308 ammo, I would ditch the interest in AR-10s because it will basically be a safe queen. For plinking, your best option is 7.62x51 147gr Swiss right now as far as cost/quality go. AmmoSeek is your friend.