It doesn't work like that. Period. End of story.
If a raw book is worth $10, how can you think a graded book would be worth
$12, when it cost about $30 to get it graded.
If a graded Batman 1 sells for $500,000, why would a raw copy sell for $100,000 less when the only difference is a $100 slab?
Many books that are graded won't bring the cost of grading, let alone the price of the the raw book plus the grading fees.
If a dealer is known for their tight grading, a raw book they call a 4.0 might sell for more than a CGC 4.0 of the same book.
In short, there is no easy answer.