Here is some research from the Tire Rack - It is a good reference
point for price. I have also included customer feedback results:

Kumho XRP $880 (Run Flats) N/A rating
Michelin PS2 ZP $1286 (Run Flats) 8.8 rating avg 220 AA A (Wear
Traction Temp)
Firestone SZ50 EP RFT $1434 (Run Flats) 8.1 Rating
Goodyear GS EMT $1288 (Run Flats) 6.6 rating
Michelin AS Plus ZP $744 (Run Flats) 8.3 rating 500 AA A (Wear
Traction Temperature) - has double the tread wear life of the ZPs


From Michelin:
PS2:
Wear Life 8
Fuel Efficiency 10
Handling 10
Braking 10
Comfort 7

AS:
Wear Life 10
Fuel Efficiency 9
Handling 9
Braking 9
Comfort 10

THere it is. You are paying a lot of money for performance on the
ZP. ZA has softer ride and longer wear.

If the AS was available when I bought my tires, I might go for them.

Bob Drake 2000 C5
>
> Thanks to both of you for the comments. *I am a little confused. Are the
> ZP's more expensive than the Pilot A/S? *Costco here wants $500 for
> the two A/S's for the front and Discount Tires wants $560 with their
> extended warranty