I agree, you should have known that this was coming. The reasoning behind failure to close isn't clear from your post, but it IS clear that this should have been dislcosed to you BEFORE closing.
Rate lock extensions are available in multiple increments - usually the loan officer takes the shortest possible that he or she expects will do the trick - for instance, if he or she thinks that it will only take 15 more days to close, there is no reason to extend for 60. If the delays in your loan were ongoing or unexpected, it is quite possible that there would be 6 extensions.
The cost of extending varies by investor, type of loan, type of lender, etc . . . usually extensions cost between .01% - .05% of the loan amount per day - that is, on a $100,000 loan, it would cost between $10 and $50 per day to extend the lock. On a $200,000 loan between $20 and $100 per day . . . etc.