On Thursday, March 1, 2018 at 3:53:52 AM UTC-5, wrote:
Rolls-Royce Trent 900: Unit cost $46 million
Engine Alliance GP7000: Unit cost $13.5 million (2006 dollars)
In this news, Emirates pays $30.5 million for the Trent 900:
$30.5 million is about 2/3 of $46 million.
Maybe it is a European thing, the RR line keeps a European company running. Also, it is always nice to have two sources of engines, in case one has a problem. If your airliner comes with only one variety of engine, and that engine gets grounded, there can be big problems. I am sure that RR has a solid enough reputation.