Once a company starts operating, but before revenue (and hopefully eventual profitability), the valuation is trickier. The share price _should_ be the number of shares divided by the sum of all future profit (minus current debt.) Which is hilarious of course, because no one actually knows the denominator.
That original $2M equity stake can grow to billions if the company ends up making something that a lot of people want or need, so the sum of all future profit is large. Or, much more likely, it will be worth nothing, or a modest amount.
Graham's essay kind of avoids the point of whether ownership of a vastly appreciating asset is "fair", if a bunch of other people help that asset to appreciate.
Another far more sensible model I've found is slicing pie. Each founder's input % of the pie pre-'bake' is their % of the rewards. And what makes up for one's slice of the pie? The dollar-value you would've earned if you worked somewhere else, times the period of baking. These can be tweaked accordingly to the type of investment put in. IMO, it seems far more grounded compared to say a flat 10%.