Yes, this is the common way to do it ($buyin + $fee), but you'll have to remember that the TD started out as a tool for my own tournaments. I added Rakes at the request of a user.
The tough part now is, if I ultimately decide to change this, how to transition without breaking all those saved tournaments out there. And there are a lot of dependencies (formulas, stats, exports, layout tokens, etc, etc, etc).