It has been my experience that when horse rescues are interviewed they over estimate the costs of feeding the horses they have in their care. I think that is for the sole reason to get people to donate to their cause.
News reports like the one below often exaggerate the costs of horse ownership.
The amount mentioned in the video for grain is not only unbelievable but most rescues do not feed grain to the horses because it compromises a horses’ system that has been starved. Grain is for horses that are worked hard and need extra energy calories, not for a slow and steady weight gain that comes from good quality hays and pastures.