Vito, I read the same thread (believe it now resides in Retail Deals and Feedback) and signed up 2 weeks ago and posted a reply to the thread as such. Yea verily, if you sign up on your own, a life membership is $1000. However, if you sign up for life membership with a sponsor, its only $300. I confirmed that several times with the customer service rep on the phone, saw the $300 charge on my card, and logged into NRA website with the membership number they gave me over the phone and set up my account. It confirmed my life member status.
Initially, they didn't provide a membership number, but I asked for it and they promptly supplied it. You need that number in order to set up your account on the website, so you can have proof of membership if you need it, since the package takes 6 weeks or so to arrive.
So, no, it doesn't appear to be a scam.
NRA Life Member