The question simplifies to, would I crack out a 1906-D $10 Eagle graded MS64 that has an 85% chance of being upgraded to MS65. So, the question is, would I bet $120 (Express plus shipping both ways) for an 85% chance to win $5750? Yes, I would. I'd keep making that bet on a diminishing argument, as well. Basically, if you crack/subbed it four times, that would give you a 99.95% chance of getting back an MS65 coin. Now, if you asked a different question of whether I believe that coin has an 85% chance of bumping to MS65, then the answer is no.
I agree that there's not an 85% chance of the grade bumping to 65. Maybe a 25% chance, though. Would you pay $120 for a 1 in 4 shot at a $5K windfall? Let's say you did it 5 times, at a $600 outlay. If each time there's a 25% chance of grading 65, then there's a 76% chance that within 5 tries it grades 65. Would you pony up $600 for a 3 in 4 shot at at $4400 profit? Presenting: The Game.
I still wouldn't view it that way, quite. I'd look at it as 75% taken 11 times = 95.7% chance of success. So would I pay $1320 for a chance of the coin coming back a 65? Yes. However that also ignores the nuances of grading. I don't even think it's a 25% chance of a bump to 65. I'm thinking this is the reality: 5% downgrade to 63 2% downgrade to 63+ 75% remain at 64 10% upgrade to 64+ 8% upgrade to 65 At those odds, it would take 36 "attempts" to net a 95%+ shot at a MS65, and even then, it's not guaranteed. So, even at 8%, it mathematically works, but it's really close to marginal failure at 36 times. If that drops to 5%, the number jumps to 49 attempts. Any lower than a 5% chance at the grade means an outright losing proposition.
Different numbers, but it's still The Game. Everyone plays it differently, and everyone has to pay to play.