// Requires a decimal and commas
^\$?(([1-9]\d{0,2}(,\d{3})*)|0)?\.\d{1,2}$

// Allows a decimal, requires commas
(?=.*\d)^\$?(([1-9]\d{0,2}(,\d{3})*)|0)?(\.\d{1,2})?$

// Decimal and commas optional
(?=.*?\d)^\$?(([1-9]\d{0,2}(,\d{3})*)|\d+)?(\.\d{1,2})?$

// Decimals required, commas optional
^\$?(([1-9]\d{0,2}(,\d{3})*)|0)?\.\d{1,2}$

// *Requires/allows X here also implies "used correctly"