Need help understanding thin lenses for progressive?

[kids optical frame]

I need someone to help me understand why some progressives have prism thinning. And the cheap prism lenses. What progressive do you recommend or suggest? In fact, the progressive lenses are too difficult to process with prism power. So most optical factory are not willing to produce this kind of eyeglasses. They strongly recommend choose two ways to slove this problem. One is that cancel ADD as single vision eyeglasses, and the other is that change lenses to bifocal glasses.