The last time this was brought up the consensus was it was not worth the extra money. Rip-off is a very bad term, as you have the option to pass. Some people are buying them, as there are plenty of sellers out there. I just don't see the need to have a bullion coin verified by a TPG.
I agree that it is a waste of money. Just what is it that PCGS is certifying anyway? "PCGS has inspected all of these coins in this tube and can attest to their authenticity. All of these coins will grade MS68. However, if the seal that keeps this tube permanently closed should be tampered with in any way, our warranty will be invalidated." (Fictitious) Chris