Moonga Tussar is spun silk yarn (broken or smaller silk fibre are sent to the mills to be spun into yarns), hence cheaper.
Since it is mill spun there could be a blending of other fibres to it also. This also explains the lint or fibre shedding from the fabric.
Moonga/Moga/Monga is being used by vendors over quite some time, to sell what a lot of consumers might interpret as MUGA, Assam’s very own Golden Yarn