I'm in NY as well and there's a place on LI that advertised the Toyos as an X5 20" staggered package on ebay... that's how I found them. Came out to about $1k installed after "local pickup".

As for the rims, OEM or replica? Replica can be bought from wheelsandcaps.com (also on ebay for the same price). Good experience. Also about $1k so together I spent $2k, which is a good $1k cheaper than OEM rims + tires according to my calculations.

And no, no runflats for Toyos... got away from runflats because of both the harshness of the ride and cost of replacement. I do have a spare because of no 3rd row.

As for treadwear, 1010tires had a good rating on these but now they don't appear anymore as they are no longer sold [as new]. It was at least a 4 of 5 on the wear rating as I recall - I looked for it to as it was an important factor. So far I'm on 4k miles and they show no signs of wear... that's all I can tell you.

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'08 X5 3.0si - Alpine White / Saddle Brown interior
Specs: Sport Pkg, Premium Pkg, Tech Pkg, Comfort Access, Aero Kit, Style 433 staggered 20s on Conti DWS
Mods: Carbon 35 tint, LED angel eyes, GP Thunder 7500k fogs, H&R 20mm/25mm spacers, clear reflectors, gunsmoke-tinted taillights
Coded: Digital speedo, windows/sunroof/tailgate close via keyfob

X5 pics at Flickr