CNBC reported that one in five consumers who purchase bitcoin do so using their credit card. Melissa Gamez purchased a used RV with $18,800$ miles for $$46,700.$ Originally the RV sold for $$69,000$ with a residual value of $$19,800.$ After subtracting the residual value, depreciation allowance per mile was $$0\mathrm{.}82.$

How much was Melissa$$s purchase price over or below the book value?