The cost of
TPG grading are about what the error coin is likely worth on the market.
If your motivation for
TPG slabbing is a way for your heirs to sell -fine.
If your motivation is flipping the coin for current cash then IMHO the
TPG costs are a waste of your money - all knowledgable collectors who specialize in error coins know what this is.
Take a look at my other hobby ...
http://www.jk-dk.art