You would usually use the term "rates" when you're paying for someone's time by the hour/day/week, or when there is a contract for continuing services (rather than a one-off payment).
For example, if you went into a shop looking for a new TV set, you would say "I'd like to know your prices". If you called a music teacher to ask about lessons you might say "I'd like to know your rates".
"Rates" can also mean interest rates, and in the UK it can refer to a type of tax on premises.