The "using Excel for inventory" seems to contradict what you originally said about customers wanting inventory plus something else. If they are already using Ex

The "using Excel for inventory" seems to contradict what you originally said about customers wanting inventory plus something else. If they are already using Excel (or Access) just for inventory than they are already comfortable having inventory in a silo. You are offering "a fancy Excel sheet on the web" which has been successfully marketed by a number of SaaS companies in other problem domains. (Time and expense tracking for instance.)