There are things on that Remington that would cost you no matter who does your AR. For example: If you want the camo like the Remington you'll fork out around $200.00 more, if you want a decent single stage trigger you'll need another $150 or more. I suppose, if your handi you can drill and tap the hand guard for accessories, if not you'll pay a per hole charge for a gunsmith to do it. Then you need to purchase special assembly tools for a kit AR ...... Yes you can make a basic AR for significantly less money, but if you want something special no matter how you do it, you'll pay more.
I was looking hard at building an AR for myself, after adding up the camo, the special barrel contour, a decent trigger, the stock and grip I liked the price came close to what I'd pay for the Remington and the odd part is the Remington is almost exactly the rifle I wanted to build, right down to the 22" barrel and contour.