I've never liked the term "net worth"; it seems to imply that a wealthier person is more valuable or important. Are there alternative words or phrases which do not have this problem?
Bill Gates's [word or phrase] is $114 billion.
You can use FINANCIAL WORTH
Definition & Legal Meaning (thelawdictionary)
This term applies to the net value of a person’s assets and property after his liabilities and debts have been taken away.
There is no defined term for FINANCIAL WORTH before liabilities and debts have been taken away.
When we weigh assets against liabilities, the result is a "balance":
4a accounting : an amount in excess especially on the credit side of an account
You could therefore write:
The net balance of Bill Gates's accounts is $114 billion.1
If it was clear that you were talking about Gates's financial portfolio, then the term could work in your sentence with no modifications:
Bill Gates's net balance is $114 billion.
1I've retained the word "net" from your question even though it's probably redundant here.