If the doctor would only be losing potential income of $7,000 maybe that's not called an expense or a loss like loss of revach from not working on chol hamoed is not called a davar haaveid. So maybe he should be mechuyav to forgo more than 20% if it's not called being mevazbeiz because he's not spending money he already has?

If the doctor would only be losing potential income of $7,000 maybe that's not called an expense or a loss like loss of revach from not working on chol hamoed is not called a davar haaveid. So maybe he should be mechuyav to forgo more than 20% if it's not called being mevazbeiz because he's not spending money he already has?