Winter wheat or rye, for a northern climate, seems to be the least expensive. Deer usually don't touch until late fall/winter.

This year I have Soya's, that I've left standing. Deer are digging through the snow... high energy from the oil, for winter survival. On a dry year though, when alfalfa re-growth is poor, I've had the deer hit the Soya's hard in August. Not leaving much for seed production. Cost is much higher then wheat.

Depending on natural food source availability, deer my not hit food plots until late, when all other sources are exhausted. Example this season deer didn't hit plots until late... only after the larger acorn crop was cleaned up!