You should also figure charter boats can be easily used 200 days a year. Virtually all those days will be 24 hour days. In most cases the boat will be heavily loaded, all the bunks, all the heads. More booze than normal will be involved. The users will be hot and sweaty much of the time. Many will have worse than no idea what they are doing. A boat in the slip at home ia used only a few days a year in most cases. Imagine leaving your boat open for all you friends to use at their will at home. Chances are the boat in charter will get far greater use coupled with island sun and salt water everywhere.