With or without the rebate, Costco offers the best deal at the present.

Tirerack.com
255/50VR19 Michelin 4x4 Diamaris.............$468.00
285/45VR19 Michelin 4x4 Diamaris.............$504.00
Road Hazard Program for 255/50VR19 Diamaris...$56.16
Road Hazard Program for 285/45VR19 Diamaris...$60.48
Shipping......................................$79. 24
Tax...........................................$ 0.00
Excise Tax....................................$ 0.00
State Waste Tire Fund Fee.....................$ 0.00
Purchase Total..............................$1167.88
Estimated Local Install/Tire Disposal........$100.00
Tirerack Total Cost........................$1,267.88

Costco.com
Michelin Diamaris 255/50VR19.................$485.98
Michelin Diamaris 285/45VR19.................$523.98
Installation/Road Hazard......................$40.00
State Tire Fee- California.....................$7.00
Disposal Fee...................................$4.00
Tire Rack Total............................$1,060.96
Shipping...................................... $0.00
Sales Tax.....................................$83.65
Total Cost.................................$1,144.61
Less Costco Discount..........................$60.00
Net Costco Price...........................$1,084.61

Savings......................................$183. 27

There's no arguing with dollars and cents. Another plus is that Costco's road hazard warranty covers 60 months versus Tirerack's 36 months.

The Michelin Latitude Tour HP's are brand new to the market (June 2006) and are billed as performance all-season tires. The treadwear rating is AA vs. the Diamari's A, treadlife is AA vs. the Diamari's A. It's probably a plusher riding tire (think more MXV4-like than Pilot-like), but unfortunately there are no 3rd party reviews that I can find on the web.