PSA tiered grading

[mferronibc]

I apologize if this has been asked before but can someone please explain to me the actual basis behind PSA charging more to grade a more expensive card? In theory shouldn’t the grading process be the exact same for any card submitted whether a $100 or $5,000 card? Do they handle higher end cards differently, have more experienced people grading them, etc. or is it literally just a money making scheme to get “their cut”? Also, when submitting a card obviously whether it’s an 8 or a 6 could really impact the value, what do you select in terms of value of the card? I mean I’d rather be paying $20 versus $75 a pop but is there ever a sense that selecting the higher tier (if you really feel a card could qualify for a high grade) could actually end up netting a higher grade? Is this part of some kinda “back door” BS that if you pay more you may end up with a better grade for the same card?