Realistically you won't find 25mm+ IW carbon wheel set for much less than $1000. Maybe $800 if you find a deal. Used, maybe $600. Don't bother to "upgrade" your wheels if it's not actually an upgrade.
That said, plenty of people bikepack with random shit equipment and have tons of fun. You might also look into "non boost" 29er wheels, which are readily available for cheap. But most will have like 22mm wide rims, and wider is nice for 45mm+ tires and lower pressures.
ride bikes, climb, ski, travel, cook, work to fund former, repeat.
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