Here are some options that are currently in stock at palmetto state armory ,
the bottom one is basically what your getting except it has a $50 stock , $24 grip and a $150 hand guard on it so add another $225 to the price , except you are getting a much better quality rifle with the PSA stuff . The top ends are all prebuilt and pop on with 2 pins , the lower needs built but really its super easy and doesnt take any special tools.
Keep in mind all of these kits are excellent and all include the C158 bolt in the BCG
Option 1 has a $400 aimpoint red dot that comes with it along with the magpul CTR stock and MOE grip
Option 2 has the nice looking MI hand guard , 18" hammer forged barrel and a nice trigger
Option 3 is the bargain basic M4 , still a high quality platform , just no fancy stuff . I have built many rifle from this platform all run 100%
All of these are well under what the guy is asking for and you get to keep your ruger . I know you will be getting a 100% quality rifle from PSA and If I was closer I would build the lower for you for nothing just to help you out and get you headed down the right road , Mags run $15-$20 DEPENDING ON THE MANUFACTURER