If buyers were using only their own cash, then you don't have to worry about what interest rates are doing. But if people of varying levels of financial sophistication are competing to purchase, and some of those people are using borrowed funds, then it implies something about how the least sophisticated buyers are going to bid.
First, it's a bit of a cliché from realtors in every area of the US to say: "It's different here". Sometimes it might be, but when interest rates and cheap money are available nation-wide, it pays to think about what that implies about prices.
If buyers were using only their own cash, then you don't have to worry about what interest rates are doing. But if people of varying levels of financial sophistication are competing to purchase, and some of those people are using borrowed funds, then it implies something about how the least sophisticated buyers are going to bid.