On April 30, Apple completed the largest corporate bond sale in history, raising $17 billion in six bond issues ranging from 3-30 years.

They picked an incredible time to do it.

10 year Treasury yields

The 30-year AAPL bonds have absolutely tanked, down 9.7% from the 99.41 sale price. If Apple were to buy back the $3 billion outstanding at market prices, it would save $290 million.

All told, the timing of the bond sale saved about $850 million (and counting), which is almost 5% of AAPL’s total annual operating budget.