SHAFAQNA – The Grand Ayatollah Shahroodi answered a question about the limit for Halal profit.
Question: What is the limit for Halal profit? (Meaning what percentage can be added to saleable goods on top of their costs in order for the trade transactions to be correct and God willing Halal?)
The Grand Ayatollah Shahroodi: This case has no definite religious rule, rather it is left to approved laws or a percentage of the usual profit among sellers, and whoever is fairer and considers the economic situation of the customer, his sustenance is more blessed and Halal.
Source: PERSIAN SHAFAQNA