Are Proofreaders Expensive?

In order to help study for the upcoming tests that I will be taking, I purchased a review book. I bought it last summer so I don't remember exactly how much it cost, but I think it was at least $50. Considering what it costs to actually take the test, it's not that much. While this book is helpful, I can't help but think that they formatted this book and then said "It's ready for print", and then cranked up the presses. You can tell that nobody actually bothered to proofread this book, and if they did, they just flipped through the pages and declared it good. The errors are mostly with formatting. Maybe they used one program to do it and then switched to another program that didn't support the formatting or something, because there are some weird symbols that show up. There are a few places where the information is actually wrong too, but hopefully anyone who has been to pharmacy school recognizes these errors. Some of the review questions also have answers that contradict information given in other places. Anyway, I think that if you're going to charge fifty bucks for a paperback book, you should probably at least make sure there are no grammatical errors. Maybe the cost of paying someone to proofread is so outrageous that it cuts into their bottom line.