A property is listed for $550,000. A potential purchaser makes an offer of $525,000, consisting of $50,000 cash and a $475,000 mortgage back to the vendor bearing interest at 7.5% compounded semiannually with monthly payments for a thirty-year term and a thirty-year amortization. Calculate the equivalent cash value of the offer if thirty-year mortgage rates in the market are at 8.25% compounded semiannually.