They might have had delivery contracts from before the prices increased, so they didn't have to pass them to customers. Maybe the last servers from those contracts got delivered already and any new orders need to be bought at much higher prices.
Another possibility: They were growing too fast and need to slow down. At some point additional growth might become too risky, or even exponentially more expensive. It might require fundamental organizational changes.
I’m not a business person, but they’re already at the “hundreds of thousands of servers” scale, what about the 41st data center be organizationally far more expensive than the first 40?
Simple example: Pizza delivery service. The company runs very well, customers are happy, demand increases. At some point the demand gets so high, that they need to buy a second car for deliveries and a second pizza oven.
They look at the numbers and see the risk of making less profit than before, if they expand. Especially if demand decreases at some point, instead of growing further. So they decide to just raise the prices, lower demand and make even more money without additional risk.