you prevent capital loss by buying the house.
However, you can't expect them to find everything including some very unusual issues, such as the hot water pipe connected to the basement toilet flush.
As for how much time they should spend in inspection with their price, that's determined by the profession's market rate (hourly).
You can't say, oh, you are charging so "high" so if you missed a few unusual issues, I'm gonna file complaint or sue you.