I just bought an LR-308 yesterday. I got the last, a base model, and as I was checking out a guy came in and asked if they had another. When I said that I got the last one, he offered more than I paid (full MSRP) for it. Yep, dealers will soon be reaping it in.
If a bill gets introduced banning them, the prices will go through the roof. Manufacturers will push production limits to get out as many as possible before an effective date if the bill goes through. Those items (receivers, mags, weapons) will all sell for more than you think is possible. Ask those of us old enough how we know.