GIS Web App (ASP.NET)

An agricultural services company needs a web-based GIS program to allow growers to view AND edit maps of their fields. The program would preferably be written with ASP.NET and would access a SQL Server Express DB. Needs to handle common GIS file types for importing and exporting data as well as allow the user to view various raster image types, especially .sid files. Program would import soil sample results from lab's FTP server into SSE DB. Growers could add crop information and see fertilizer recommendations. Basically just trying to get a ballpark idea of what this might cost...