1955 Roberto Clemente Rookie Card:
"Strictly graded" Mint $40,000
PSA Slabbed and Graded Mint-9 $478,000
..and these results are more or less typical up and down the board.
PSA has found the goldmine..and sportscard investors are eating it up, and have been for several years.
I'm sure Doug Smith can tell you how much his vintage unopened material has increased in value in just the past few years. Likely 5 to 10 fold.
This being said, there are maybe 1-2% of casino chip collectors as there are sportscard collectors..and that is being generous.
I don't think slabbing and grading of chips is a good idea, and would never be beneficial on any sort of scale..