[LincolnVT]

I know that it varies some by player, era and population, but I'm wondering how people go about calculating the value of various PSA or SGC cards. Is there a rule of thumb out there?

For example, take a SGC NM-MT 1948 Leaf Jackie Robinson...say that one sold or was to sell for 100k (made up number) what would the price break be on the same "make and model" of Jackie Robinson in say a SGC EX, SGC Fair and SGC A holder? Also, how would you calculate the value of a SGC Mint copy based on the NM-MT being worth 100k. Obviously, these numbers are always changing based on the most recent auction results.

It seems to be toughest to calculate the current market value of ultra rare cards / postcards / items graded by SGC and PSA that don't have recent auction results...any thought on these types of pieces?

Thanks.

Ethan