To soon to tell since many of the cars are repaired out of warranty. However, the parts are fairly cheap online considered that this car(2015+) is only a few years old. The price of parts usually get cheaper as the car ages. Dealer sourced oil filters are cheap($7) in my area. The car uses standard engine oil and gear oil, however transmission fluid is a bit costly($10 a quart or more) like any other luxury car.
I personally have cheaply repaired some interior parts that was worn like the gear shifter indicator trim(bubbled window) and shift knob(peeling chrome). The shift knob was $30 new, and the perfect looking shift indicator trim was about $40 used on eBay.
Aftermarket brake pads and rotors are priced fairly cheap for a luxury car with large brakes.
The car seem fairly easy to maintain for a luxury car overall.
The most expense wear parts of the Genesis seems to be the active suspension shocks which are $500 each from the dealer new. There are no
aftermarket replacements for them yet. Also, the seats are expensive to replace as well at about $1000 each.