Is it normal to have to pay for a Practicum?

My fiance will have to complete a carpentry practicum in the summer. He's being charged the normal amount for a class. He already has a job and that will count toward his practicum. Is it normal to have to pay several hundred dollars to get credits for the practicum?

That's a good question. It depends on the program.
Ten years ago many things were subsidized, included in the whole program's cost, or offset by the value of work produced.

In carpentry, it seems students would be making money for a company immediately, without the overseer spending too much time training.

The school and coordinating faculty would incur costs for processing paperwork, coordinating mentoring carpenters/businesses, assessing the employers' evaluations, and possibly meeting with students periodically through the practicum.
But that should not be the full cost of a course, unless the courses were cheaper than other schools. Some schools offer pre-practicum courses, and have to pay faculty for the whole before-during-after process.

Talk to the school about it, especially since using his job for part of his co-op/practicum credit. And pray that God will find solutions that make it easier on you.