I can see arguments both ways
1 - DONATE THE DIFFERENCE TO CHARITY
2 - FLY WITH NON CPL FI TO KEEP COSTS DOWN
Just highlighting the ethical aspect of this, no real axe to grind either way.
I Just think that the current system is unethical where client pays full whack and PPL FI fly's for free (although I suspect that clubs do pay FI regardless of CPL or PPL).