Pricing for a PSA/DNA Certified Authentic (autographed) vs. a Graded PSA

[MCoxon]

All - any rules of thumb for how to value a PSA/DNA signed card, graded A, vs. a PSA numerically graded card?

An example would be, say:
- 1955 Topps Ted Williams PSA 6. SMR=$350
- 1955 Topps Ted Williams PSA/DNA. SMR=?

I'm sure there are situations where the difference between a graded and a signed card is bigger or smaller, depending on if:

A) the player is alive or deceased. I'd bet a deceased PSA/DNA would be closer in value, maybe more expensive than, a highly graded number. Example: 1967 Topps Maris PSA/DNA worth more than a 1967 Topps Maris PSA 8

B) the card is rare or common, e.g., a 1959 Bazooka Mickey Mantle PSA/DNA vs. PSA graded, as opposed to 1969 Mantle PSA/DNA vs. PSA graded, given there are so many more 1969 Topps Mantles and so many fewer 1959 Bazookas.

I have a specific card I'm looking at...

other thoughts? thanks, mike