What is the ruling on profiting 40 piasters from each shoe piece when taking on its manufacturing at a price of 1.30 liras and giving it to workers for 90 piasters, with the workers being informed beforehand of the expected wage without their knowledge of the excess profit?

There is no harm in giving work to another party for distribution at a lower wage than what is taken from the factory, if the person is not acting as an agent for the factory and takes the work in his own name and for his own account. This is considered a sub-lease. Their assumption that you are giving them the work at the same price you receive does not affect the contract, unless that was due to deception on your part. It is better to inform them that you are profiting from the work.