Cant upgrade items if all slots full

Lux, 4 full items and 2 large rods, therefore full inventory, want to upgrade the rods into the wizard hat and have 1100 gold (1300+ actually), the game wants full price, 3600 or so, despite displaying the 2 large rods components checked. Because the game wants full price I cant upgrade. Later, after selling one of the rods I am able to upgrade (not sure if I lost money on that, but was the only way).

This should not be necessary however.