I have often heard that the grain and cob is 1/2 of the yield in silage, I would suppose that if you took 40-50% of the silage dry matter yield you would be in the ballpark. 20T silage x 35%DM = 7T DM. 1/2 of that would be 3.5T, snaplage/earlage is normally harvested at 65% Dry Matter(35% moisture), 3.5 divided into .65 = 5.38 T as-is. This is all speculation, the only way to know how much you have is to weigh it and check moisture.

Can't help you with value/Ton, some seed corn books have charts for bushel of corn per ton of cob corn at various moistures.

You could look at value/acre for silage, ear-only should be worth nearly that much with an adjustment for stover value-not too many $$, but something. Or charge for the shell corn and figure that giving up the cob and a little stover offsets some drying costs. You will also have the field available for manure application or fall tillage sooner than dry corn harvest.

Just some ideas, pick and choose what you like.