Another person has proposed this before but I can't find who he is
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I think over it the other day and find giving Luck a small income bonus/penalty may also help. The appropriate number should be somewhat similar or slightly less than growth, e.g. +/-2%.
It's not unrealistic - luck help making money. People can still use Order +3/Luck -3. But with the income bonus/penalty acting against each other, it's a self-defeating setting. I have no problem with Order +3/Luck 0 as you have to spend points to get the bonus.