Can the verb "purchase" be used with an abstract concept such as language course, considering that they money were actually paid so it isn't a free course? Is it okay to use it in a formal email or better to write "enroll in a course"?

Can the verb "purchase" be used with an abstract concept such as language course, considering that money is actually paid so it isn't a free course? Is it okay to use it in a formal email or better to write "enroll in a course"?