There's an old joke where a man asks a woman

M: "Would you sleep with me for $1M"

W: "for $1M dollars? Yeah, I guess I could be convinced for $1M."

M: "What about for $10"

W: "No, what do you take me for!"

M: "We've already established that, now we're just haggling over price."

I don't think this is that funny of a joke, but the point I'm making is that picking a number is a detail that comes after we decide that there needs to be a number. And I think if you agree that there needs to be a number, the gov't is the one that could set it (or the voting public).

The most likely answer is you pick some multiple of minimum wage, and then some number of years at that number. 1000x minimum wage, 10 years of earnings at that value. That's the maximum you can have. You want more? You gotta raise minimum wage.