Basically, the additional value of the certification needs to be at least as much as the raw cost + cost of certification. That's not just purely value, it also attests to the guarantee of genuine.
Say you show me an 1916D Merc dime, raw. You swear it's genuine and AG3. You are probably a fine, upstanding honest citizen, and an expert coin grader, so you are correct. And on
ebay, they have sold in the range of 363 (ANACS) to 550 (PCGS). I'm still not going to pay you the 550.
But if you can buy it for $450 and spend $35 to have it certified, there's room to make money in there...
-----Burton
50+ year / Life / Emeritus
ANA member (joined 12/1/1973)
Life member: Numismatics International, CONECA
Member: TNA, FtWCC, NETCC, EveryCountry (online) coin club
Owned by three cats and a wife of 40+ years (joined 1983)
Author: 3rd Edition of the Sample Slabs book,
https://www.sampleslabs.info/