I agree that DAL doesn't want to spend more on instructors than they have to, but Nosmo has a good point - the B747-400 sim is in MSP, but the base is in DTW. Unless the B747-400 instructor lives in MSP, he's taking a hit by commuting to MSP to instruct. If they move the 330 out of MSP as well, same problem.
Not a problem at DAL since ATL had all aircraft based there. I guess if the 765 moves up to NYC, they'll have the same problem (well, mostly since I imagine a lot of ATL guys will commute to NYC for the $$$, leaving a lot of potential instructors in ATL)