Many people look around for or cheap funeral packages. Low-cost undertakers offer a set cost for different package funerals. In this case, it is not always possible to change the coffin. Sometimes the cost is not set, but as already mentioned plus Disbursements.
Generally, costs include a coffin. If you were to purchase a coffin as discussed in Step 3. COFFINS and decide to decorate it, you would be best advised to inform the undertaker of this when you book one of their packages. You can then ask how much the reduction would be as you are supplying the coffin and not them.