Certainly they are worth whatever someone is willing to pay for them. I am not one of those people.
Here's the way I figure: It comes down to what you are going to record on them. If you are taping a CD, for $16 you could just buy the CD new. By that logic, I don't know why anyone would want to record a CD to cassette at all- just buy the CD! If you are taping MOST records, again, you could buy the record for less than $16.00. Now if it is some super rare record that is worth a lot more than $16.00, OK. If you are taping radio, a $16 metal tape is WAY overkill! Where I could really see a use for a high dollar blank tape is live recording. Then I could easily justify paying $$$ for a quality blank tape. And it doesn't get much better than a TDK MA-XG.
That's my $0.02, or $16.00!