When I bought my OEM winter tire/wheel set, I paid about $1450 ready to install with TPMS, wheels, tires, mounting, balancing, etc. I think the price has gone up since then, but surprisingly, the dealer isn't all that bad for some things. For example, the winter tire package all inclusive is cheaper than buying just the wheel as a repair part. No good reason why, but it is, or at least was true when I bought mine. When it comes time to replace my winter tires, I'll probably try the Nokian R3 tires verses the Bridgestones, though. Just bought a set of those for my other car, but it's too early to install on it and try them out.
NOte, the i3 wheels are forged, not cast, so that they are lighter and stronger for their size than a cast one would be...that costs more.
2011 535i x-drive GT, 2014 i3 BEV