Massive Discrepancy in Trade-In Value

I am Google Fi customer and have been considering getting the Pixel 9. For existing FI users it's $250 off. When I add my old Pixel 6a for trade-in I get an abysmal value of $84. Out of curiosity I checked on the regular Google store, and lo and behold the trade-in value for the same device when buying the same Pixel 9, is a staggering $225. That's quite an insane difference. And it mostly kinda negates the better offer for existing Google Fi subscribers.