What is the average cost for a dog autopsy?

miniature pincher born 4-18-2004, died unexpectedly, need closure, died Sunday yesterday at 7 am. I really want to know the cause of his death so i can have closure. showed signs of discomfort for 2 days but still was eating and drinking water. Not sure if he had a bowel movement saturday. was planning on waiting to take him to vet on monday as my vet is closed on the weekends.

My vet said that since it has been morethan 24 hours, the liklihood of results were pretty low. I am in the medical field and find this hard to believe. Wouldn't they be able to see inflamed organs, poisioning, or major cause still?