An imaginary one, I reckon. Summit Racing Equipment's online catalog lists the most expensive Flowmaster exhaust kit at around $540.00 - for a late-model Corvette. Most other applications list at prices between $150.00 and $350.00. Now, if you go look at the Borla product listings, there are three which approach or exceed $1,000.00 - kits for the Corvette, Viper and (!!) Chevy Monte Carlo. Of course, Borla's stuff *is* high-grade stainless steel and for all practical purposes *permanent*.
Even if you also replaced every gasket, bolt, nut, hanger and even the catalytic converters, it would be tough to nudge a Flowmaster system cost over $1,000.00.