$150 for a textbook? it’s virtually free, said the parent of a pre-med student 
First year chem was $500, which was $300 for the text (not used of course, not available), another $100 for the lab workbook + access code, and $100 for study guide and solved problems or what have you. Organic Chem was a steal at $300 and Calc I at $200, as they’re reused for Orgo 2 and Calc 2 respectively. Typical book fees are easily $800 a semester for us.
The access code for homeworks online is pretty sinister as it kills the second hand market or online sellers.
How much authors make? not a whole lot. Much of it goes to the publisher.