is is just a conjugation of being the more correct saying would be: the cost is 5 dollars.
I think "cost" is one of those weird words that is the same in past & present tense. Hence: It cost billions of dollars.
yes
It is correct to write it that way. Free is without charge and seminar means there will be discussion.
No, you must say I was in London yesterday.
No. Say "in the amount of ten thousand dollars."
I would say it cost about $30 dollars but for 2 people it is about $50 dollars
In the US, we use Dollars as the term. The correct way to clarify USD, for example to make clear that they are not AUD or NZD, etc. would be to write or say US Dollars. You can write or say United States Dollars, but few people do because it is much longer-winded.
I would say 5-10 dollars an hour.
Yes, I would say that sentence would be grammatically correct.
No, the correct way to say it is "be a human being."
You could say 'it is 100 dollars less than you were supposed to pay' or 'your payment was 100 dollars short of the total amount.'
According to many stores say they cost between 19.00 & 50.00 dollars.