In the bigger scheme of things McLaren sell roughly as many cars as BMW sell i3s, i.e. a rounding error in global auto sales.
McLaren got there first in making carbon fibre tub a road going reality, for the super-rich, just as they did on the track in the world of F1 almost four decades ago.
The i3 costs about as much as the brakes on a McLaren. Not that there's anything wrong with that, it's just an odd comparison to make.
If you're looking for a way to attenuate somebody's enthusiasm about BMW's amazing, relatively cheap carbon fiber process, it's that BMW is publicly downplaying its importance in favor of aluminum. That's either about production costs or about complicated problems of meeting passenger car safety standards with carbon fiber, depending on who you talk to...
> McLaren got there first in making carbon fibre tub a road going reality
The i3 is actually a carbon fiber body-on-frame design relying on aluminum. It's wild, but definitely not something McLaren would want to use for a 700-hp sports car.
[0] https://en.wikipedia.org/wiki/BMW_i3#Marketing_and_sales [1] https://www.forbes.com/sites/nargessbanks/2018/05/29/mclaren...
Meanwhile, every review about the Model 3 (LR and Performance) shows that the 3 series and the M3 don't appeal much. And the Model Y will be shown in a few months to compete head to head with the BMW X3 and X5 in a few months.
It's a proof of concept, and a way to test the market before really committing to sustained production of electric cars. BMW could produce other electric cars in volume if they decide the market is viable.