I've only had cards graded a couple of times, once to crossover cards from GAI because I was reading things that made me wonder whether the grade was accurate or whether I should have them examined again by another party.
Also sent in raw cards because I actually do like them in slabs, for protection purposes. I also think they display well in slabs, like little pieces of art
I have cards graded by the top three in my collection (SGC, BVG, and PSA) and I have some that I keep in their raw state just incase I need to feel or smell a card
So, for me, I would grade a card that I thought would get at least a 40, or a 3- I think that would be worth the money spent (for the type of card I collect, T206)......and mainly for protection purposes as well as handling and display purposes. I've damaged modern cards trying to pull them out of old penny sleeves
and I surely don't want to damage a 100+ year old card.
Sincerely, Clayton