Very interesting points raised. Great post. However, I think one of the multipliers should be modified:
That's very true. But a better way to figure this into the calculation is not to make a modifier based on the amount of time it takes to run it, but to pay yourself what you think you can get for your time elsewhere and add that to the costs. Therefore the initial profit number (to be modified) will be = revenue - hosting costs - your hourly wages.
It may trivial but the difference is important. Suppose you value your time at $25.00 an hour. If a site's profit (before taking into account your wages) is $100 but requires 10 hours a month to run, then clearly the true profit is -$150 dollars because your time is worth more.