I am not understading your query, Since both are different Law and act, which case law can i provide. please let me know what exact query from Sales
Since your following Sec.4A MRP scheme under Excise obivously the abate ment can be taken because MRP may or maynot include the margin also but excise will apply on the value before adding the margin which is produced value but sales tax is not like that is on the sales value including Magin
Also VAT will applicable on excise duty (which is Product value plus excise duty)