You have to ask yourself, if the price is so cheap, WHY its cheap. ;) Crap trims here are 25 dollars because otherwise, those poorly skilled farriers would have no business. They get business based on a cheap price, not skill. They don't keep knowledgeable horse owners as clients because of the shoddy sub par work. They prey on new and uneducated horse owners and develop "reputation" based on long term relationships with people who don't know any better.
SOME times, people who have been with good farriers a long time will get cheap prices because they are loyal. SOME times good farriers will work with people on limited incomes to help the horse and the person. It depends.
Good trims here are 35 to 45 in general. Sometimes bad trims cost that too though. Educate yourself and utilize the powerful tool in the internet at your disposal for other opinions and advice if you are not yet educated in what a good trim is and go from there. JMO.