What is the highest worth item to resell?

Solution 1:

a crown sells for 250,000 bells and a royal crown sells for 300,000 bells

Solution 2:

Coelacanth, Great White Shark, Dorado and Stringfish sell for 15k bells each.

Solution 3:

Found the whirlpool bath, which resells for 32,500 bells:

32,500 bells whirlpool bath