Without wanting to light blue touch paper, in our case the preference of employing crews with a TR is a timescale issue, not a financial one. The time it takes to type rate a crew member is often longer than a crews notice period. The trend at the entry level crew market is to bugger off with very little notice when one of the big boys offers our crews jobs. We had one situation a while back when the crew was offered a job on a Sunday if he could start 8 days later. For us we pay more to a TR'd crew, so there is little financial advantage, it's more about keeping continuity of crewing.
Phil