Actually, even a non-profit has most of the same overheads that a for-profit organization has. So some insight into what the for-profits actually do might be useful here.
And THERE IS a rule of thumb for that. An engineering business bills at 2.5 to 3.0 times actual labor cost. A jewelry store charges 3.0 times wholesale. So does a furniture store (unless it's Costco LOL).
Why? Because there is insurance, payroll taxes, utilities, etc... all the same things a properly run non-profit faces. But there usually isn't volunteer labor, home baked cookies, that sort of thing. Thus whether it's a homeowners association or a non-profit association of business executives, you GOTTA charge at least 2.0 times your identifiable actual direct costs to cover the indirects, repairs, unexpected expenses, etc...
And 2.25 is better if your paying audience will pay it.
So that's my recommendation - 2.0 to 2.25 times direct costs. Kinda puts an emphasis on getting stuff that would otherwise be a direct cost DONATED, doesn't it? As well it should.
Hope these thoughts help.
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