Owning gear is expensive. Acquisition cost, maintenance cost, insurance, storage. While it would stand to reason that by eliminating those costs you could parlay the savings into rentals, the truth is that the rental house is going to amortize all of those costs out into the rentals.
I still think you can make it work, but the math is very simple. Take your average gig, price the rental to our favorite supplier, and see what you have left.
We own quite a variety of sound systems, but we don't own a large concert array system. I did the same math you are doing and found that, on average, I can get a 10 or more percent discount from my supplier on gear and production staff, I can mark it up 5% or so to the client, and make more money than I would have made if I owned the gear.
My supplier does more concerts than I do, they do them more efficiently and better, so they make good money when you spread it out over more gigs. More gigs for them, less gear to own for me, more money all around.