In return for that 7%, you don't get your principal back. Right? Recently I was buying credit union CDs for a guaranteed 5.1% and I am getting all my principal back at the end.

I'm sure you could do calculations that would compare the value you get if you invest say $200K this way, 7% per year for 25 years and you don't get your principal back in the end, to the value you get if you invest $200K for x rate of return over the same period but you do get your principal back.