The reward of $10,000 is equal to about $230,000 in 2018.
Gold was worth $20.67 per ounce from 1879 to 1932. Five hundred pounds of gold is 8000 "avoirdupois" ounces (the weight the US uses), or 7200 troy ounces (gold is measured in troy ounces). This would put the actual value about $165,000 or $149,000. A gold shipment worth $125,000 would be about 400 pounds.