Add a "warning" message in ArcGIS Online that notifies users they are about to consume a large amount of credits. For example, "Be careful! You are about to execute a process that will consume "x" credits. You will have approximately "x" credits left in your account if you proceed. Do you want to continue?"....yes/no.
ArcGIS credits are a nebulous concept for most people, and we do not necessarily know which processes are credit intensive.