You're looking at it wrong. Let's say that diesel is $80k new, hemi is $70k. When you go to sell them in a few years that diesel will be worth $50k and that gas will be worth maybe $30k. As long as the diesel resale value is above $20k it will fetch far more then the extra amount it cost new. No one wants a used 2500/3500 gas truck. You cannot give them away. A used few year old diesel? Most dealers can't keep them on the lot and if in good shape command a massive premium.