Cheapest I have seen for a 2.5G adapter (1899/-) :-
Limited-time deal: Wavlink 2.5G USB C and USB 3.0 Ethernet Adapter, Hybrid 2-in-1 Network Adapter Compatible with USB C/Thunderbolt 3 or USB 3.0 Laptop, Aluminum Portable USB-A & Type-C to RJ45 Adapter https://amzn.in/d/duB2iBf