That's not a record or even close !
This one...a gelding(1) cost US$15.m - which is about 8.8m gns - my eyes fell out of my head: http://horsecountrychic.blogspot.co.uk/2013/09/want-to-see-what-15m-horse-looks-like.html
I thought I'd read somewhere that racehorses are not insured, as they are worth so so so much money but in such a high risk sport/ catagory, so no company will cover it. Did I imagine that?