If you don't care about cost and only want the best, that is true.
I put almost 300,000 miles on my last ford truck using only conventional oil or tier 3 oils. I never spend the money for the Amsoil. That engine was perfect, not even a slight ticking sound. No leaks, anywhere and I never had to remove the valve cover or oil pan. I sold it to someone that is still driving it today.
Now, over that same amount of miles I could have used a tier 4 oil and got the same results but I would have spent an additional ~$1500 for the price of their oil. To me, I don't see the benefit.
I recommend that you do what I have done. Choose a oil that is in your budget and after that oil is drained from your vehicle, send a sample to Blackstone Labs for a an oil analysis. I was told that by changing oil every 5000 miles on that particular vehicle is causing no wear. Therefore, Amsoil would not have been better. Now if they told me that the traces of metal are too high which means my oil was not doing its job, I would have chose a different oil or shortened my oil change interval. Where tier 4 oils shine is when you decide to go way over your oil change interval. There are also special condition like motocross when they do dry starts at the gate and launch immediately with zero idle time, tier 4 oils should be used.
If you are worried about sever riding conditions and think your tier 3 oil won't hold up, just check the manufactures viscosity charts. You will find the viscosity rating for 150°C for most oils. If you get your engine oil up to 150°C or 302°F you will probably have more issues to worry about. But, you can choose a oil that has a higher viscosity at those higher temps.