Amazon shares sunk more than 9% on Friday after the company’s hefty spending forecast surprised investors who were already wary that the artificial intelligence boom is at risk of becoming a bubble.

The e-commerce company on Thursday was the latest tech giant to announce plans for a massive increase in capital expenditures, after Google parent Alphabet, Microsoft and Meta all signaled they expect their spending sprees to continue.

Amazon, Alphabet, Microsoft and Meta reported about $120 billion in capital expenditures in the fourth quarter alone. That figure could exceed more than $660 billion this year, the Financial Times reported, which is higher than the gross domestic product of countries like the United Arab Emirates, Singapore and Israel.