Why does a "civil" Marriage Celebrant's cost vary from one paid to a Religious Celebrant?

A "civil" Marriage Celebrant has far more flexibility in regard to the time of day, the venue for your wedding and the ceremony content than that which can be offered by a Religious Celebrant.  This means that a "civil" Marriage Celebrant devotes a considerable amount of time to you and your ceremony not to mention that there may be some travelling involved:  something that is not usually the case with a Religious Celebrant.  Another important difference is that your "civil" Marriage Celebrant is not being paid a wage by a church or other religious organisation and furthermore, Marriage Celebrants are also required to pay for overheads necessary in running a small business (which may include GST) and, of course, income tax on the fee you pay them.