If this were an unknown start-up, this headline could justifiably be accused of being clickbait. But Ming Yang is one of the world's biggest wind turbine makers. Furthermore, they've already tested this 'double-turbine' design with a 17MW prototype. So if they claim 'half the cost', then it's believable.
It makes sense, too. How much is one extra turbine going to add to the overall cost of a project? Not much, but it's doubling the output.
This illustrates a trend with renewables that other energy sources can't compete with. Technology keeps dramatically improving renewables all the time.
China’s Ming Yang promises monster two-headed, low cost 50 MW floating wind turbine