Hi,
If I developed the application using the developer's version, it would be difficult to sell the application with MSDE as the backend to a customer, because the customer would have a difficult time doing adm like adding users, setting roles and privileges, and adding new columns, tables, databases, etc, without buying the minimum configuration of the the actual MSSQL.
Of course, if the application is written for a client that has already purchased MSSQL, there would be no added cost in selling a MSSQL application above what is charge for the application itself.
LelandJ