A diagnostic MRI of the skull for a dog opposed to a human might be the cost of I.V. sedation or anesthesia. Then in human medicine the MRI is done at a fee but there is also a fee for the radiologist to read those films, you may not be including that cost in a human MRI. You're probably also thinking of a part of the spine, a knee or shoulder which are smaller areas that take less time.

Then there is the difference of contrast versus no contrast. For the skull-brain, they might want contrast used which is an additional cost also.

I do think the possible added cost is the I.V. sedation which a human doesn't typically need. A dog can't be told to lie completely still and not move such as a human can. Then someone is monitoring the dog's vitals, their respiration and heart rate . There may be an anesthesiologist fee for that. I'm not sure but it sounds likely.

So sedation, the person that observes the dog during it and possible contrast may be the extra costs not involved with a human possibly.