Xiaomi's latest flagship series repair costs revealed: A motherboard replacement could cost nearly as much as a new Redmi K70. The Xiaomi 15 Pro's curved display and advanced camera system command premium repair prices compared to the standard model's components.https://www.notebookcheck.net/Xiaomi-15-series-repair-costs-outside-warranty-revealed.912751.0.html
Replacing the motherboard for any phone out of warranty is cost prohibitive because the motherboard represents at least 60% of the manufacturing cost. People don't replace the motherboards of phones that are out of warranty because it makes no sense economically. The only two parts of a smartphone that people typically replace are the battery and the display. Realistically that's nearly all that most phone shops can even fix without replacing the entire motherboard.