Dealer offering premium package w/ blind spot,comfort package,navigation package,parking assist and preferred accessory pkg. for $49,439 - $5,000 special savings for selling price of $44,439 before tax, title, dealer service fee and registration. When I look at invoice numbers at different sites, I come up with $44,071. My last Lexus ( 2008) I got 15% off MSRP. This is only 10% off. What should I be able to negotiate down to.