They have not said anything about upgrade cost till now. Did they ask 1k in your case? Which mouse did you RMA?
I also asked about other options and they gave these.
(1) Razer DeathAdder V2 X Hyper Speed Wireless Ergonomic Gaming RZ01-04130100-R3A1.
(2) Razer Basilisk V3 - Ergonomic Wired...