I’d compare total cash outlay up to your most likely moving date, not automatically over 15 years. Include upfront fees, monthly payments, any early-repayment charge, and the loan balance still outstanding when you sell. Run several dates if your plans are uncertain. APR is useful for an initial...
I agree on completed sales, but I wouldn’t dismiss the 18 days entirely if it persists across several neighbourhoods. The useful split would be homes selling without a reduction versus those cut early to secure a buyer. Financing may also affect buyers differently across such a wide price range...