Is anyone else really frustrated or having the same issue that I'm having that Ebay is miscalculating shipping costs to the buyer? 

Yes, I think it is affecting some others.

Not that I am a seller. But there was someone posting here the other day about a different issue but he had said this in one of his feedback comments,

Your system failed, once again, postage costs higher than you calculated Do u actually get anything right in your procedure?

Obviously, the comment was aimed at ebay, so it would seem he was having the same issue.