The 6 degrees of separation is a myth: great product fail because they never find their way in front of the public eye.
Distribution is everything, branding is everything. Get your name out there, whatever it takes. The best distribution is of course word of mouth, which is why your initial pricing doesn’t really matter.
The most powerful growing products to 3 things at once: they make you look smart to the people you invite, they give real value to you when the people you invite joins, and they give real value to the people you’ve invited once they sign in.