Sale price is the current sale price not the buyer price. Meaning if you get a key from somebody it still look like a purchase. I know because I sure as hell did not spend $797.54 on my 99 games.
These prices aren’t all that accurate. Looked up my account and I payed $49.99 for Skyrim when it came out and it says the current price of 29.99. But interesting none the less.