Had to dig up some historical domain sale and found two sites:

DNSalePrice.com - very very slow, but lots of history

NameBio.com - slick, but only 20% of the data on DNSalePrice.

I was really surprised that so few resources exist for this market. It would seem prudent that sites like Sedo and TDNAM would want everyone to know current sales prices. Either it is too much work, or they are worried expectations will rise even more, cutting out on their bread and butter, sub $1000 sales.