Why Are PSA Slabs Worth More Than Other Grading Companies?

Despite the good reputation of BGS, SGC and CSG

Ok, so, a PSA Gem Mint card, a BGS Gem Mint, a SGC Gem Mint, and a CSG Gem Mint all walk into a bar.

The PSA slab says, “I’m more valuable than all ya’ll!”

The BGS responds, “Oh yeah, well I used to be almost as valuable as you!”

The SGC pipes up, “Yeah, so what, I’ve got a loyal following too dude! Who cares I’m three quarters your going price!”