I'm doing an AR build right now, mainly because I don't like what's available for sale right now. You can't find anything already assembled with quality billet 7075 matched receivers, premium parts and a sleek, lightweight handguard / rail system. And, if you could find this, they are asking $3K+
At least I have a spare barrel lying around, a premium bolt carrier and some lower receiver parts lying around to get me started. It's still going to take me awhile because of the cost of some of the stock and rail systems I want to use. I'm just going to take my sweet time after I have the lower assembled with stock.