Wow, I think I watched the price rise in front of my own two eyes: I visited the page, and saw a sale price of $441.10 (6.5% off) and eventually went to the same page in another browser and saw $471.76. Refreshed the first page and there's no longer a discount.
At $441.10, that would make it $1,764.40 for a set, which (assuming they include the TPM sensors) is pretty close to the $1,739.32 (including a random $4 "fee"(!?)) for a set from Tirerack with the Rial X10-I wheels. One thing I find interesting is tire rack specifies the tires in the kit were manufactured in 2015. That seems 'old' for a product that degrades with age if you're still selling it as 'new'.
If you're ok with settling for the 427 wheels, these seem to be the cheapest option I've found at $1,482.36 (excluding shipping)
https://www.shopbmwusa.com/PRODUCT/6528 ... Id=9671701