Can I use these interchangeably?
How much did that cost?
How much that cost?

Question

Answer

For the past -
How much did that cost?
How much did you pay?

For the present -
How much is this?
What is the price of this item?
What is the cost of this item?

Answer

How much that cost? (No)
What did that cost?
What was the cost?
How much was that? 
The last 3 don’t have identical meanings but they are properly formed questions.

Answer

How much did that cost? - correct
How much that cost? - incorrect