I priced out a top of the line Mustang GT Premium yesterday to get an "idea" and it came to $33,400 after adding every option I could as close to the SS2/RS Camaro.
Take that for what it's worth.
2009 Challenger R/T - Arrington Forged 6.0L and Magnacharger Supercharger - 600RWHP 600RWTQ (PB E.T. in 1/4 Mile 10.85 @127.39MPH)
2016 Hyper Blue 2SS Camaro (PB E.T. in 1/4 Mile 12.093 @114.43MPH bone stock)