i dont know how complicated it would be to write up the code that lets users categorise the sale, but if every sale item was appended a sequence like
GTR--20K25K--SYDNEY, i.e model-separator-startprice-endprice-separator etc
then people would be able to search
+"-GTR-" +"20K" (that will return both 15K20K and 20K25K) +"-SYDNEY-"
but the codes have to be strictly outlined, and appending of code mandatory for first coupla months
this is very simple implementation wise, but ppl may think it tacky, - prefer carpoint interface and search options!