gzt: 
Servicing is required every 12 months or 20,000km, whichever comes first. Service prices are as follows:

12 months/20,000km: $190.37
24 months/40,000km: $504.25
36 months/60,000km: $190.37
48 months/80,000km: $661.32
60 months/100,000km: $190.37
72 months/120,000km: $504.25
84 months/140,000km: $190.37
96 months/160,000km: $661.32

Based on what I've learned about this the reason for the higher cost every 40,000 km is due to a coolant change. 

As context, the 2019+ Kona and Niro are similarly afflicted and the reason in their case is down to using a very-expensive "low-conductivity" coolant that Hyundai put in place as a rolling change. The basis for moving to this coolant type is that several crash test EVs in S. Korea caught fire some hours subsequent to the test. You can find these events with a google.

If you look under the hood of the Ioniq 5 there are two coolant tanks that I'm speculating is the result of them minimising the volume (and therefore expense) of coolant that circulates through the battery pack.  I'm not clear if Kia did the same with the EV6. 

So, perhaps it's the same thing with BYD? I'll add that my 2018 Kona service costs have been $220 a year while under the short 3 year warranty so the lessor BYD services of $190 don't look that bad in comparison. It has standard green coolant so I'll just have to hop out a bit more spritely in the event of an accident, as Tesla owners would as well.