Is grading worth it?

The sum is short. The graded price at the grade you will probably get, minus the raw price you could sell for today, minus everything grading costs, times the probability you actually get that grade.

Every term is knowable except the last, and the last is where the money is lost.

Getting the graded price right

Look up completed sales for the card in each grade separately. A 10 and a 9 are different markets, and the gap between them is frequently much larger than the gap between a 9 and a raw copy. Pricing your submission off the 10 comps is the optimistic error.

Getting the expected grade right

This is the term people ruin. Cards look better in the hand than under magnification, and the difference between a 9 and a 10 is routinely invisible without a loupe and a straight edge. Centring in particular is measured, not judged, and it is the most common reason a card that looks perfect comes back a 9.

Assume the grade below the one you expect, run the sum on that, and only submit if it still works. If it only works at a 10, you are not making an investment, you are buying a lottery ticket with a postage cost.

When grading is worth it almost regardless

• Authentication. Above a certain value the slab is buying certainty that the card is genuine, which is a real service independent of the number on the label. See what grading does to the price.
• Liquidity. A graded card sells faster and to more buyers, because the buyer is not judging condition from photographs.
• Protection. If you are holding long term, the case is a good case.

When it is clearly not

A common card in any grade is a common card. Grading certifies condition, it does not create demand, and no grade turns a card nobody wants into a card somebody wants.