Dead Heading Crew is very cost effective for the company up until the point crew dislike it so much they resign.
When a policy of Dead Heading crew was introduced into Gulf Air there were initially 3 complete crews (39 soles) daily deadheaded Bahrain to AUH. This resulted in a 05.45 am sign in and a 7.00am dead head....(to ensure they were legally fatigued) to perform AUH midnight takeoffs to...Indonesia via a KL landing. To CDG via FRT. And to India via MCT.
Soon more crews were dead heading before flights ,after flights, and into joining blocks, and dead headed to different blocks...you never knew or eventually cared who the heck was arriveing on your flight deck or doing the business down the back...you could bet your mortage the nationals and goers would be on the easier trips and the rest got the hard trips.
The real killer is the GF Mark 2 version of dead heading....crews are split up down route to min crew numbers... and the rest dead headed as required.
I once went on a 5 day block three days before Christmas Eve and was required to remain and operate via deadheading for 17 days...my commanders voyage report on this 5 day block extended to 17 days was simply "not believed by my fleet Captain" who had it checked out....there was no pay for my mainly night flying on my rostered days off...as I had not been called out from base.
I think the crew option is to go sick down route (not fatigued) if rostering spring this one on you too often.