The crew can tell from the electronic manifest if it's an operation upgrade, a staff ticket or the original ticket is a redemption, but not anything more granular and the fare paid certainly isn't visible. I would be very surprised if most cabin crew even look at this area on their iPad / phones since with ther reduced staffing level they are more busy than usual particularly at the start of the trip. Mostly I think crew would regard a customer as a customer, and don't really have the time to over-think it.