Free: Contests & Raffles.
The reason there are so many Ruger upgrades is because they're necessary.
I have not shot the S&W AR's but I have a Bushmaster. I don't consider myself an expert by any means, but I don't personally see the benefit to paying more for a S&W when the bushmasters and others will do everything they will. I have nothing against S&W, they make some damn fine guns. Some are just a little pricier than others. And building your own is something I have considered as well. Once again, I'm no expert but I'd buy another Bushmaster before I'd buy a S&W.
Bushmaster or Remington made by Bushmaster.