It's also a really naive calculation in that it assumes you will be able to fill nearly every working day out of the year with a full day's worth of paying work. When are you going to pursue leads, develop your sales funnel, learn new tech, and file your taxes?

Um. You work for money. Generally one should have a target amount of money in mind (based on a budget). I rather like the calculation. I'll use it next time I do consulting.

Do you think this is how companies price their goods?

I mean, sure you should calculate a bare minimum rate. But you should charge as much as the market will bare.

Of course you should have a budget, but what does that have to do with the value you're providing as a consultant?

If you're asked why your hourly rate is $X, are you going to reply "because I have expensive hobbies?"