20k face value maybe on rounds worth $40 each

this isn't as insane as it sounds. bullion coins are legal tender with a lower face value than their commodity value.

so if that's 20k face value it's about average value for a house and they probably used the legal tender number for tax purposes.

But when it comes to paying 3rd parties like in the OP you're better off just selling the silver and using the common currency ... so no $2 bills