It goes without saying in EVE, skills matter, implants matter, better facilities matter.
I have no mining implants at this time and my skills are ok (not maxed).
This is my results after a long mining op.
8137 Plagioclase (compressed).
68.3 yield NPC station
~55,800,000 ISK sell ore
~50,700,000 ISK sell minerals
Player station (Athanor)
Sell ore ~55,800,000 ISK
Sell minerals ~54,800,000 ISK
Refine cost; 991,958.10 ISK
The difference is 48,293 in Mexallon, at 70 ISK per unit is 3,380,510 ISK profit ONLY counting Mexallon, minus refining cost 991,958 = 2,388,552 more in profit.