From what I understand, one skyblock.net diamond is equal to around $2k- $3k in .org money. Let's say $2.5k on average. Since $1 = 10 diamonds, and 10 diamonds would mean $25k on .org, I'd say that $1 could get you around $25k. Although I could be totally wrong as I rarely play anymore, just trying to give you an approximation.
Honestly, I think there is no set rate for ORG money to USD. The reason for that is simple: There are so few upgraders. I remember one person offering to upgrade me, and that was 500k for $10.