The warlords are explicitly rich beyond anyone else's dreams. This is reflected in how they're portrayed and in the dialogue and plot. The Bullet Farmer has guns. Lots of guns. While everyone else is using crossbows and dart launchers and hand to hand weapons he's blazing away with machine guns because he's rich. He's the guy who makes the bullets. The People Eater is corpulent. He's the guy who makes the gasoline. He's the guy who refines the oil. He's got a cracking plant built in to his giant limousine tanker. And he's a bean counter - During the whole chase he's keeping an exact count of all the machines and fuel used up. And Immortan Joe, of course, has the water. He's got water, he's got food. And because of that he has a massive fleet of well equipped vehicles with the soldiers to crew them.

And look at their vehicles. The Giga-Horse, the Bullet Farmers car-tank, the People Eater's limousine. Rictus Erectus' monster truck. Even Nux little VWish thingy, it's his car. He's modded it to hell and back. He can drive full speed in reverse, or keep going on three tires.

All the detail is baked in to the film. It's all there.