Question 1

Why do I get "Too Expensive" at the anvil?

Accepted Answer

Each anvil use adds a prior-work penalty. Combining books and items in the wrong order pushes the cost past the level cap. The optimizer finds an order that avoids that.

Question 2

Does it show the cheapest combine order?

Accepted Answer

Yes — it returns a step-by-step anvil order with the estimated XP cost.

Enchant Optimizer