If you are a head of state / billionaire who thinks they need this level of protection, you're gonna trust the security & reliability of some random rental outfit in each city you visit? Zero chance.

Excess is relative. When you have $$billions, $150K extra to have your custom protection vehicle at the venue is no big deal. And, are they even rentable in all locales, and do you trust those suppliers?

I am with you - while this might seem excessive there are enough people that have the cash and the threat model to go with it.

From what I could find the 2009 Protection version (then called high security) was more around 400k-450k€. A standard model 7 runs from ~115k up to ~145k€.

Yes, I must say that I love BMW's approach. Everyone else just takes a frame and hangs off of it all the protection — just a massive increase in redundant weight and decrease in performance.

Far better to take BMW's approach, upgrade the materials so that the protection is structural; each component serves both purposes.