Check Tirerack.com. $123.00 per tire for Dunlop SP5000 Sport. This is the OEM on my 2003 LS430. I think it is a great tire. Had no problems with noise or ride.
I have a 2003 ls430 with Dunlop tires. It is my first Lexus. I think it is a new model Dunlop this year. The tires are excellent and very quiet. Don't know how they will wear yet.