License for Spatial analyst Server side use in a web based tool

Discussion created by purid on Aug 22, 2012

I am developing a tool which will be published on web but it will process the feature on server side and deliver the results to client. I am using Spatial Analyst Extension to calculate Elevation from DEM as part of a complex model. My question is - Is there another level of license to accomplish this (As compared to buying Spatial analyst Extension for ArcGIS desktop) and approx. how much can it cost additionally??