In 2018, Bill Gates' net worth was approximately $90 billion. His estimated income was around $12 billion, according to estimates from Business Insider.
In 2018, the median net worth of an American household was $101,800. I chose median cause these billionaires drastically skew the mean. The median household income was $63,179.
If an average American household gave the same scale of gift in 2018, based on household income, the gift would be $83.29, and based on net worth, it'd be $17.89.