1. You're scared to charge what you're worth.
Number 1 is the biggest failure point that I've seen otherwise good business owners make. Think about it. Your plumber won't show up for less than $70. Neither will your electrician. They've perfected their craft, licensed, and insured themselves. How many hours of you screwing up the job is a one-hour, $70+ visit worth?
Playing music for weddings is similar. I haven't played one in a while, but my rate was 2-3 times the going rate for a church service. I always showed up for the rehearsal (to lower the risk of surprises), and often ended up buying additional music for the service.
I'll make an exception for charging less than the going rate. I will provide my services for free. That means that I know you well enough to give you my services as a gift, or you represent a charity that I would like to donate my time to.
Don't muddy the waters by doing a "favor" and charging less. The recipient will still have had to pay you, and won't see the benefit that you provided as you do. At the same time, you will have received less than your normal rate and not necessarily receive the amount of goodwill you expected.
Charge what you're worth. If you're not worth a reasonable rate, then you probably shouldn't be in that line of business, at least for yourself.