Are you kidding? How could anyone afford a Bar Mitzvah teacher after all those expenses?
I’m willing to bet that, with a little work (assuming you are in a large enough community), you can find someone to teach the Haftorah (and maybe even the laining) on a reduced-fee (or even free) basis.
The Wolf (who, in almost thirty years of teaching has never turned away a student for lack of money — but do you really want an apikorus like me teaching your twelve year old?)