For the big airliners, it's cheaper to do in simulators. However, if
you ever sat in one of those things, you'd really hvae to keep
reminding yourself its just a simulation. These things are so real, its
easy to forget it. If paying passengers are not on board (what we call
part 135 or 121 operations) we can and do go up in planes and practice
things like shutting down one engine, slowing the plane below minimum
flying speed, making very steep turns, go arounds, etc. The smaller the
airplanes, the more likely these are done in real airplanes (because of
the cost of the simulator vs the cost of flying the plane for
non-revenue).

-Robert