I redeem the vast majority of my points in a city where I get 1.3c/pt on average. When I can do 5th night free it ends up being 1.63c/pt. This is before factoring in the points you'd earn booking with cash, which brings the net value down since if you get a $900 + tax room for 85,000 points, as a Titanium you're losing the 15750 points you would have earned.
I'm actually getting 2.35c/pt there later this year due to a combination of waived 3rd person fee on awards, 5th night free, and all nights being off-peak points even though cash rates are the same as usual.
I would never redeem below 1c/pt. At that point I'd always pay cash and use the points for a higher value redemption.