​How can I find out what an owner paid for a property?

[Quandra Adams]

I have ran the comps for a property and submitted an offer and got counter offered. I am convinced that the seller is asking too much for property. I had my agent ask for the comps used to determine the price and the buyers agent sent over 4 year old comps. It probably really doesn't matter much but I'd really like to know what they paid for the property. We wrote in the contract that the sale would be contingent on an appraisal and I may have to accept their offer to find out what the property is worth. How can I find out what the owner paid for the property?