That depends on where he's getting his parts...

Over the counter, a belt will be approx $25, a tensioner $50, maybe another $40 for seals if those are included.

The discount web places will do a belt for under $10 (although the 93- seems to be more, a bit under $20), a tensioner for under $30, and seals for maybe $25.

As far as the tensioner is concerned, personally (I do my own timing belt changes BTW) I replace it with every 2nd belt, or with the first t-belt change on a vehicle new to me if I can't find documentation of when it was last changed. It is after all just a wee bearing, it wears. Usually after 2 t-belts (100K mi) it just starts to become a bit unsmooth - time for change. Once the t-belt is off anyway it's maybe another 2 minutes to change it on a 4-cylinder engine.

Bram