I think , How much is it ?

2 & 3 are fine

1. This is used when something has already been purchased. (Note the past tense "did cost".) you might ask this to a friend. This can also be "What was the price of that?" "How much did you pay for that?" 2 and 3 are equivalent. They would be used if you were in a store asking about the price or to another person when you want to know the price before purchasing. Also as "what's the price of/for/on that?" There are many more colloquial expressions. "What did that set you back?" "What's the damage?" "What would someone have to pay for that?" as examples.

Most would say "How much is it or if you are both looking at the object simply say how much as you know what the item is.

The best to say while asking for the price is "how much does it cost?"